Last update: December 12, 2023

Emergency: Performing a Fish-in Cycle The RIGHT Way

Uh oh!

So, you just bought your new fish and are only just now learning about this cycling thing…

Or, maybe you are following the terrible advice of the pet store employee who said you only need to run your filter for 24 hours before adding your fish.

Maybe it’s even worse. You killed all the good bacteria in your tank and have to cycle your aquarium all over again.

Don’t worry! These scenarios are much more common than you think.

If you can’t return your fish, then you have only one option:

You have to cycle your aquarium the old-fashioned way – with fish in the tank.

Today, I am going to show you how to successfully cycle your aquarium with fish inside.

If you haven’t bought your fish just yet, I recommend using the fishless cycle, which is an easier, faster and safer way to cycle your aquarium. Interested? FishLab’s fishless cycling guide will walk you through the process.

What is fish-in cycling?

The purpose of a fish-in cycle is to kick-start the nitrogen cycle, an invisible three-stage process where beneficial (good) bacteria establish themselves in your filter, keeping your fish safe from ammonia.

I cover the nitrogen cycle in much greater detail here. If you are new to the hobby, it’s worth reading because an effective nitrogen cycle is perhaps one of the most important parts of a healthy tank.

For the rest of you, here’s a quick recap of the nitrogen cycle in action…

Waste breaking down into ammonia, nitrite and nitrate in aquarium diagram

Stage 1 Waste such as pee, poop and uneaten fish food break down, releasing ammonia, a toxic chemical, into the water.

Stage 2 Beneficial bacteria eat the ammonia and release nitrites, yet another toxic chemical.

Stage 3 A second type of beneficial bacteria eat the nitrites and convert them to nitrates, which are harmless in small amounts and are removed from your aquarium each time you perform a water change.

Important: With just a single letter separating nitrites and nitrates, it’s easy to confuse the two. Remember… Nitrites are highly toxic to your fish while nitrates are not harmful in small amounts.

Just one problem…

There aren’t any beneficial bacteria in a brand new aquarium. And without it, toxic ammonia and nitrites build up, causing serious harm to your fish…

So, it’s up to you to kick-start the nitrogen cycle. And to do that, you need some help from your fish, well from their pee and poop.

As the poop breaks down, it releases ammonia and encourages the beneficial bacteria to appear.

You might have noticed a flaw in this…

If ammonia is harmful to fish, and you are using your fish as a source of ammonia, doesn’t this harm them?

Well, that’s exactly what brings me to my next point…

Why shouldn’t you use a fish-in cycle?

In an emergency, a fish-in cycle might be your only option. If that’s the case, cycling with fish is perfectly acceptable because your fish might die if you don’t.

But if you have a choice, then you shouldn’t be cycling your aquarium with fish inside.


Well, a picture says it best…

Goldfish floating upside down dead inside fish bowl

Yep, fish-in cycling is very stressful for your fish. And, many fish won’t survive the process. Those that do are often more susceptible to disease and live shorter lives.

I assume you want to keep your pet fish alive as long as possible, right? Well, a fish-in cycle is a terrible way to start.

So, why is a fish-in cycle so harmful to fish?

Well, during the cycling process you are waiting for beneficial bacteria to establish a colony in your aquarium. And once they do, they will be able to eat ammonia and nitrites as quickly as they are produced.

Just one problem…

While you are waiting for the bacteria to grow in numbers, your fish are going to be exposed to elevated levels of ammonia and nitrites. Even at low levels, these toxic substances can stress and severely irritate your fish.

Not only that, but a fish-in cycle requires delicate planning and leaves little room for error. It’s not exactly beginner-friendly.

Now… I’m not trying to say that fish-in cycling doesn’t work. It certainly can. But considering the obvious harm that it can cause your fish, it should only be done in an emergency.

To be honest, given that you can now cycle your aquarium without fish, it’s puzzling to see the dated fish-in cycle still being recommended.

So, why do people continue to give the advice that it’s okay to cycle your aquarium with fish in it?

I was chatting with my local, big-box pet store the other day, and the employee was preaching the wonders of fish-in cycling. I would also like to point out that he was trying to convince me to buy fish to go with my new aquarium.

The reason was pretty clear… An extra sale. A pretty scummy move, right?

But in other cases, the advice to cycle with fish is much less sinister.

You see, fish-in cycling is how your grandparents would have cycled their tank. Yep, this method has been in use for that long. In fact, this was the only way to cycle a tank back then.

In these instances, the advice to go with a fish-in cycle came from the best of intentions, people passed on what they learned years ago. You can’t fault them for that. But you can fault them for not keeping up with the times! Fortunately, you now know better!

Look, I’m sure some of you are going to disagree with me on this. Maybe you have successfully used a fish-in cycle hundreds of times without harm. That’s cool too…

But for a beginner, a fishless cycle is by far the best way to go. And in this case, a fish-in cycle should only be used when absolutely necessary.

The secret to successfully cycling with fish in your tank

I’m going to let you in on a little secret…

You can tell whether your fish-in cycle is going to be a success or failure before you even begin.


And, it all comes down to the number of fish you have in your aquarium.

More fish = more poop and pee

Since this waste breaks down into ammonia, your ammonia levels are going to rise rapidly.

And the faster your ammonia levels rise, the more harm done to your fish.

So, what is the correct number of fish to use in a fish-in cycle?

Overstocked fish tank with too many fish

Obviously, this aquarium is too small for the number of fish…

The larger your aquarium, the more fish you can include in a fish-in cycle.

Rule of thumb: One fish for every 10 gallons of water.

So, if your tank is 1 gallon, only 1 fish. If your tank is 58 gallons, 5 fish.

Don’t know your tank size? Use FishLab’s gallon calculator.

But what if you have more fish than should be in your tank?

Ideally, you want to do one of the following:

1. Give your fish away – Either return your fish, give them to a friend or contact your local fish club to see if anyone will take them.

2. Buy a larger tank – Buying a larger tank will increase the amount of fish you can cycle with.

But what if neither of these is an option?

Well, unfortunately it’s time for you to make a judgment call.

Do you try and cycle your aquarium with all your fish inside and risk killing them all?

Or, do you euthanize some, giving the rest a much greater chance of survival?

It’s a tough decision that only you can make.

Decided to euthanize? Please read FishLab’s guide to humanely killing fish. If you have to do it, please do it correctly.

Essential products to perform a fish-in cycle

In addition to your fish, tank and equipment like filters and heaters, you need two very important products to ensure that your tank is cycled correctly…

1. An aquarium test kit

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The problem with the nitrogen cycle is that you can’t see it. The only way to monitor the cycling process is to test for it. And to do that, you need a good aquarium test kit.

I recommend buying a master test kit like the one pictured above because it includes all the test kits you need to cycle your aquarium at one low price.

To learn how a test kit works, check out FishLab’s aquarium test kit guide.

2. Water conditioner

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Or more specifically, Seachem Prime. I consider it to be the best aquarium water conditioner available.

Get to know this product. During a fish-in cycle, it’s going to be your best friend.

Seachem Prime serves two purposes. The first is making your tap water safe…

You see, tap water contains chloramine and chlorine, two chemicals. Not only are these chemicals toxic to fish, but they also kill that beneficial bacteria. And without that, your tank won’t cycle.

Fear not! A dose of Seachem Prime to your tap water before adding it to your aquarium will dechlorinate your water, making it safe for the beneficial bacteria and the fish when you finally add them.

Seachem Prime also has the added benefit of neutralizing ammonia, nitrites and nitrates in your aquarium for 24 to 48 hours, making them harmless to your fish.

With these two products on hand, you are now ready to begin.

How do you perform a successful fish-in cycle?

Before I continue, I want to make one thing clear:

The lives of your fish are at stake!

It’s important that you carefully follow this guide. Read each step twice if you have to. Make sure you completely understand what you are doing before proceeding.

I cannot guarantee that your fish will survive the cycling process – some are more sensitive than others. But by following this guide, you give them the best possible chance.

When it comes to fish-in cycling, you have two choices – cycling with Seachem Prime or with water changes.

A) Fish-in cycling with Seachem Prime

If you are a beginner or are just looking for the easiest way to perform a fish-in cycle, then choose this option. This method uses daily dosing with Seachem Prime to render ammonia, nitrites and nitrates harmless to your fish.

The advantage is that you will perform fewer water changes.

Jump to these instructions for a Seachem Prime fish-in cycle.

B) Fish-in cycling with water changes

If you want to use fewer chemicals, you can perform a fish-in cycle just with water changes. This method uses the diluting effects of fresh water to keep ammonia, nitrites and nitrates at a low level.

Note: This method of fish-in cycling still requires a bottle of Seachem Prime or other water conditioner to dechlorinate your tap water. It’s also nice to have on hand in an emergency – in case something goes wrong.

Performing a fish-in cycle with Seachem Prime

Step 1: Set up your aquarium

It’s time to set up your aquarium. And, that includes all the equipment – heaters, filters, air pumps… Get it in there! Don’t forget to rinse it with fresh water first!

The beneficial bacteria need a surface to cling to, namely your substrate and filter media. So by setting everything up, you give your bacteria as many surfaces as possible to cling to.

Add water to the tank, and don’t forget to dechlorinate it with your water conditioner first.

Finally, you want to keep all electrical equipment, such as heaters, filters and bubblers, switched on throughout the entire cycling process. Not only will this keep your fish as comfortable as possible, but it will also make your tank cycle faster.

Want to cycle your tank as quickly as possible? Check out FishLab’s tips for speeding up the cycling process.

Step 2: Adding your fish

Before you add your fish, you want to acclimate them first. This will give them the best chance of survival.

You want to feed your fish throughout the cycling process… You don’t want them to starve!

When feeding your fish, however, it’s important that you don’t feed them too much. The more you feed them, the more they are going to poop. And the more they poop, the faster your ammonia levels are going to rise.

Also, remove any uneaten food from the tank, a good aquarium net will make this easy. Any uneaten food left behind will break down into ammonia, causing the levels to rise.

If a fish dies during the cycle, remove it from the aquarium ASAP. Its decaying body will also give off ammonia. Don’t panic if one of your fish dies. It doesn’t necessarily mean that all your fish will – this one might have been extra sensitive.

Step 3: Test, test, test, and test again

Now, use your ammonia test kit every 24 hours.

What you are looking for is any sign of ammonia. Trust me. It won’t be long before it appears.

Once your test kit returns positive for ammonia, it’s time to move to the next step.

Step 4: Dealing with ammonia

Once you detect ammonia, it’s time to start dosing with Seachem Prime. Follow the instructions on the bottle to determine what a single dose would be for your tank – the larger the aquarium, the more Prime you will need.

Fortunately, a little goes a long way, and many of you will find that a single bottle of Prime will get you through an entire cycle.

For this method, Seachem Prime is the most important ingredient. You see, a dose of Prime will bind ammonia, nitrite and nitrate for 24 to 48 hours, making them harmless to your fish.

Picture Seachem Prime locking up ammonia, nitrite and nitrate in a jail cell for up to 48 hours. While in the cell, these nasties cannot harm your fish. However, once their time is up, and they are released, they will once again attack your fish.

It is for this reason that you need to dose regularly with Seachem Prime, to keep these nasties locked up.

A single dose of Prime will treat up to 1 part per million (ppm) of ammonia. Prime can be dosed up to 5 times safely. So, 2 ppm of ammonia can be treated with two doses of Prime, 3 ppm can be treated with three doses, and so on.

Anything less than 1 ppm should be treated with a single dose. Between 1 ppm and 2 ppm, two doses. You get the idea. Oh, and it goes without saying that it’s better to overdose than underdose.

Once your test kit reads 2 ppm of ammonia, you should perform a 50% water change. This should cut your ammonia levels roughly in half.

Repeat this process until you notice that your ammonia levels are not rising as quickly as before. Typically, this will take a week or two. When this happens, you are ready to move to the next step.

Bookmark this page so that you can easily find it when you are ready for the next step!

Step 5: Nitrites start to appear

Next, you need to test for nitrites. If none are present, keep repeating the previous step and testing for nitrites daily until you get a positive result.

Now that nitrite has entered the equation, you need to make sure you are dosing with enough Prime to protect your fish from both ammonia and nitrites.

Fortunately, working out your new dosage is pretty simple – just add your nitrite and ammonia readings together.

Let’s say your test returns the following…

Ammonia0.25 ppm
Nitrite1.5 ppm

Adding the two together will give you a total of 1.75 ppm. A double dose of Prime will take care of it.

This time, if your combined ppm of ammonia and nitrite reaches 4, perform a 50% water change.

Keep repeating this. You will eventually notice that your ammonia drops to zero. This is a good thing – bacteria are eating the ammonia as quickly as it is being produced, resulting in a zero reading.

Continue daily dosing and testing for ammonia and nitrites. Once your nitrite levels stop rising as quickly, you are ready for the next step.

Step 6: Nitrates appear

Now, you want to test for nitrates. If none are present, keep repeating the previous step and testing for nitrates daily until you get a positive result.

Once nitrates are present, you are nearing the end (woohoo!). Continue testing for ammonia, nitrites and nitrates. Your ammonia levels should still be zero, and your nitrite levels should be declining.

Keep dosing with Prime until both your nitrite and ammonia levels are zero. At this stage, the beneficial bacteria are eating them as quickly as they are being produced.

Congratulations! You have successfully completed a fish-in cycle.

Performing fish-in cycling with water changes

Step 1: Set up your aquarium

It’s time to set up your aquarium. And, that includes all the equipment – heaters, filters, air pumps… Get it in there! Don’t forget to rinse it with fresh water first!

The beneficial bacteria need a surface to cling to, namely your substrate and filter media. So by setting everything up, you give your bacteria as many surfaces as possible to cling to.

Add water to the tank, and don’t forget to dechlorinate it with your water conditioner first.

Finally, you want to keep all electrical equipment, such as heaters, filters and bubblers, switched on throughout the entire cycling process. Not only will this keep your fish as comfortable as possible, but it will also make your tank cycle faster.

Want to cycle your tank as quickly as possible? Check out FishLab’s tips for speeding up the cycling process.

Step 2: Add your fish

Before you add your fish, you want to acclimate them first. This will give them the best chance of survival.

You want to feed your fish throughout the cycling process… You don’t want them to starve!

When feeding your fish, however, it’s important that you don’t feed them too much. The more you feed them, the more they are going to poop. And the more they poop, the faster your ammonia levels are going to rise.

Also, remove any uneaten food from the tank. This, too, will break down into ammonia if left behind.

If a fish dies during the cycle, remove it from the aquarium ASAP. Its decaying body will also give off ammonia. Don’t panic if one of your fish dies. It doesn’t necessarily mean that all your fish will – this one might have just been extra sensitive.

Step 3: Test, test, test, and test again

Now, use your ammonia test kit every 24 hours.

What you are looking for is any sign of ammonia. Trust me. It won’t be long before it appears.

Once you notice ammonia building up, it’s time to test your aquarium twice a day. And, you need to make it a routine. If you leave the house during the day, morning and night are fine.

Step 4: Water change after water change

You want to keep the ammonia levels low, at a tolerable level for your fish. So, 0.25 parts per million (ppm) or less is your goal.

The moment you notice the ammonia levels reach 0.5 ppm, you want to perform a 50% water change. That is, remove 50% of the water from your aquarium and replace it with fresh water. Don’t forget to add the dechlorinator!

What this does is remove some of the ammonia from your aquarium, diluting it and lowering the levels.

Now, just how often you need to do this entirely depends on the size of your tank and how many fish you are cycling with.

Some of you might only need to do a water change twice a week, but others might need to do it twice a day. That’s fine. Let the test kit determine how often to do a water change.

Keep this up for at least a week before moving to the next step.

Bookmark this page so that you can easily find it when you are ready for the next step!

Step 5: The first beneficial bacteria appears

After a week, you will notice that your ammonia levels are not rising as quickly as they were before. This is a good sign that the first beneficial bacteria has entered your tank and is eating the ammonia, helping to keep the levels down.

To make sure that this is the case, you now want to test for nitrites. So, use your nitrite test kit. If it comes back positive for nitrites, congratulations!. You are in the first stage of the nitrogen cycle, but your work is far from finished…

Don’t worry if you don’t see nitrites yet. Simply repeat Step 4 and continue testing for nitrites until you do. Be patient. Remember… Fish-in cycling takes a lot longer than fishless cycling.

Step 6: More water changes

If anything, nitrites are more toxic than ammonia. You want to keep nitrites as close to zero as possible. And to do that, you must continue performing water changes.

Continue monitoring your ammonia and nitrites on a daily basis, and perform water changes when your nitrite levels rise.

Keep doing this for at least another week before moving to the next step.

Step 7: The second beneficial bacteria appear

After another week, the nitrite levels should not be rising as quickly as they were before. This is a good sign that the second beneficial bacteria is beginning to grow in your aquarium.

To make sure, grab your nitrate test kit. If it returns positive for nitrates, celebrate! You are on the home stretch.

Again, it can take longer than a week for nitrates to appear. Just keep repeating Step 5 until your nitrate test indicates that they are present in your tank. Patience, patience, patience. Did I mention patience?

Step 8: Continue testing and performing water changes

All that’s left to do is to keep testing, monitoring your ammonia, nitrite and nitrate levels.

If your nitrate levels creep over 40 ppm, it’s time for a water change. Although if you are performing water changes to keep your nitrites low, I’d be surprised if your nitrate levels ever reach this.

Continue this process until both the ammonia and nitrite levels read zero on the same day. Remember, the entire cycling process can take months. So again, be patient.

What’s next? Life after cycling


You did it!

The beneficial bacteria in your tank are in high enough numbers that they can eat ammonia and nitrites as quickly as they are produced.

It might have taken a long time, but trust me, it was worth it!

Your tank is now safe for your fish. Any fish that survived deserve a medal of honor because they made the tank safe for any new fish you want to add.

On that note…

If you want to add more fish to your tank (assuming your tank is large enough), wait a week before adding a maximum of three. This gives the bacteria a chance to adapt to the increase in waste and grow in numbers to deal with it.

Still want to add more fish? Wait another week and repeat.

And remember, from this point on, nitrates will consistently build up in your aquarium. This is a major reason why we perform regular water changes – to keep the nitrate levels low.


Phew, you did it. I knew you could!

By cycling your aquarium, you give your fish the best possible chance to live a happy and healthy life.

Once the nitrogen cycle has started, it consistently runs in the background.

But you are not home free just yet…

You still need to regularly monitor your ammonia and nitrite levels to ensure that nothing goes wrong. I recommend that you include testing your tank as part of your regular water change routine.

Do you cycle your aquarium with fish inside? Let me know in the comments below!

Ian Sterling

Ian Sterling, founder of, began his aquarium journey over 30 years ago, driven by a deep fascination for fish and their diverse personalities. His website,, is dedicated to making fishkeeping accessible and enjoyable, offering beginner-friendly guidance, expert insights, and a community for aquarists to connect and share experiences.

Comments (608)

Wish I’d seen this article before I started. Into week five and nitrites just appearing but was ill informed at pet store. Started with 4 fish ( buy 3, get one free). Now have 2. Will know better next time.

Hi Jomardeuse,

Thanks for sharing your experience! I’m sad to say that this is not uncommon. That’s why finding a good local fish store, with knowledgeable staff is essential in this hobby – for a beginner, keeping fish is more complicated than it first appears.

I’m currently on my 3rd week of a fish in cycle.

I re-homed 4 danios from a friend who no longer wanted them, and at this point knew nothing about ‘cycling’ a fish tank, or really much about fish, except that new tap water should be de-chlorinated.

The fish lived happily for a little while, then 1 got poorly and died, then a 2nd, and then sadly a 3rd.

At this point I knew something was up and then started to research about coldwater fish, and low and behold found out about cycling.

I basically started again with the last remaining danio. I bought a new tank, filter etc… and started the cycling process.

I have a quick question…. My ammonia levels have lowered over the 3 weeks (currently 0.25ppm), however the nitites and Nitrates are really high, above the acceptable level.

Will regular water changes keep this under control, aswell as allowing the beneficial bacteria to establish?

I add aquarium salts, and some good bacteria, but it seems to be a slow process, and just worry for my last remaining fish.

Any help / reassurance appreciated.

Hi Amy,

Unfortunately cycling your tank is never instant it can take weeks or even months – patience is key. I know this can be hard when you have fish dying before your eyes but hang in there!

It sounds like you are nearing the end of the second stage of the nitrogen cycle. Here is a chart from the last time I cycled an aquarium. As you can see, the nitrites build up before slowly dropping in number as nitrates begin to appear. You are nearly there! To get a greater idea of where you are in the cycle, perform daily checks with your aquarium test kit for ammonia, nitrates and nitrites.

Performing water changes will help keep your nitrites and nitrates down. Just be mindful that don’t want to remove all the nitrites, as your colony of bacteria needs this as a food source. Make sure you test closely.

You got this!

I use products with bacteria in them to get a head start. Works pretty well for me. I also use a product that helps protect fish from nitrite spikes. It helped save my fish when my bacteria colonies died and I had to rebuild them. Plants can also be a good way to keep ammonia, nitrite and nitrate down. From what I’ve read floating plants and those little moss balls both work pretty well. Floating plants can get CO2 directly from the air instead of the water which helps them clean up the water more.

These days I almost never change the water in my main tank due to a large number of plants. I monitor the water closely though.

Hi Katherine,

Thanks for sharing your experience! Sounds like you have a pretty advanced setup – especially if you are able to go weeks without water changes.

Bacteria in bottles or tablets are totally useless. Proving that it makes the cycle shorter has never been done. It’s only to make you give the money. It’s a waste of your money. If you don’t believe me, try to find researches on the duration of the cycle with the all dead bottled bacteria, and without.

Thanks, my daughter is planning on taking a fish up to college with her in a few weeks. She decided on getting a juvenile pictus with her. She set up a new tank with a sand substrate since he didn’t seem to like the gravel in the community tank. He loves the sand but she read you should totally replace it every two weeks but wouldn’t that slow down the cycling of this new tank (we added lots of yucky filter juice and quick start to try to speed up this new tank). She tests constantly, and is doing frequent water changes with Prime and Stability. He seems to be happy.

Two questions…the pet store person grabbed the little guy with a net and he was stuck. It looks like he has a fin fracture on one if his dorsal radials. It turned white and he got a little white bump on the fin but everything else looks fine and nothing is spreading. Do you need to do anything to treat it? He is swimming fine.

Second, should she take Sigmund home on Thanksgiving break? It’s only 4 days. I doubt the water temp will drop below 70 even if the RA turns of the heater. I figured she could put one of those vacation bricks in. She thinks it would be better to take him home (3 hour trip). What do you think?

Hi Susan,

Most of the beneficial bacteria lives in your filter. Only a small is found inside the tank itself. If your filter is rated for your tank, properly cycled and your tank isn’t overstocked, swapping out the substrate shouldn’t cause the tank to crash.

Even so, two weeks for swapping over a substrate sounds both excessive and hard work. Most fish keepers I know stir the sand and use a gravel vac to keep the surface clean. Breaking off a prong from a plastic fork and taping it to the end of the gravel tube will allow you to both stir the sand bed while whipping up any gunk sticking on top without sucking up much of the sand.

If it’s a physical injury, all you can do is leave it to repair naturally, paying extra attention to keeping the tank very clean and water parameters normal – there isn’t such a thing as casts for broken fins.

Most well fed fish can happily survive a week and often more without food – in the wild your fish wouldn’t have a regular meal time, and may only come across a meal every few days. Best way to test this is to do a trial run, skip feeding him for 4 days and watch closely to how it fairs. If you plan to go down the vacation block route, do the same – many users report that the block fouled up their water, killing their fish.

I’d still recommend buying an aquarium heater. It’s not the temperature itself that kills fish, but rather the rapid temperature change – the temperature in a small tank can drop and raise quickly, causing stress.

I do not know about the cycle and till I buy 20 gallons tank, fish and substrate. I have over 10 fish die gradually. I test my water in pet store, they finally all come out good after 6 weeks but eventually all fish are dead except 2 coral cat fish. I am not using that tank because I want to start over again. now I use a old turtle tank for remaining 1 catfish. it is 10 gallon, I restart the cycle. in beginning the ammonia is very high, then I do 100% water change, it is 4 days ago, now the ammonia around 1ppm. no trace nitrite but about 40ppm nitrate. the tank just set up about a week. should I do another water change again? does my cycle done? I put some water and decoration from a exist dirty 2 liter fish tank with fish inside and add to this new tank. I read on line and says it will help to speed up the cycle.

Hi John,

If you have performed a 100% water change during cycling, then it’s possible that you have removed the all the nutrients needed for your beneficial bacteria to grow, stalling or even restarting the cycle. If that’s the case, you are back to square one and will have to try again.

I have a betta in a 5 gallon. First fish ever. Now I know I put him in prematurely, but I am reading as much as I can and testing daily to keep him healthy. I have been getting ammonia readings 0.5ppm on once daily testing (no nitrites or nitrates yet) and have been doing a 30% water change daily (with added water conditioner). Is that too much or too little? I’m wondering since the bacteria need ammonia as a food source and I’m always removing it, how can they really take hold? I did add the recommended bacteria supplement on initial set up.

Hi Amy,

As long as there is ammonia in the tank, beneficial bacteria will eventually begin to establish. Unfortunately, this can be a very slow process. My last tank took me almost a month to completely cycle. Is the 0.5 ppm measurement before or after you are performing the water changes?

Before the water change. I test, then change 30% if I am seeing ammonia. I have been waiting 24 hrs to test again.

It might be worth testing after the water change, to make sure that the levels are not dropping down to unreadable levels. The results you read before the water change might be due to it building up over the day.


I’m doing fish in cycling with prime as per your instructions, should I still normal weekly water changes through the process?



Hi Amy,

If you find yourself doing a water change before the week is out, there should be no need to perform a weekly water change.

Hello I am hoping you can help me. I’m at a loss. I just recently started my first tank. We had them when I was little but I was never responsible for them and back then no novice really knew anything about the nitrogen cycle. I started researching early and went to our local aquarium store. On August 10 I set up a 15 gallon freshwater tank using Aqua Life Complete water conditioner. They also told me to get to cheap hardy fish to start my cycle. They also had me add Aqua life activate along with my 2 Glo Fish tetras. There are also 3 live plants.On August 16 more Activate was added. Then I tested using API master test kit on the 22nd. pH was 7.6, HRpH 7.4, Ammonia .5ppm, no No2 or No3. My friend who keeps fish told me to do a 50% water change at this point. I also added a bubble wall. On the 21st I did have some bacterial bloom which cleared up pretty quickly. Tested on the 24th and got these differences Ammonia <.25ppm still no Nitrites and now 5.0 nitrates. Exact same thing on the 28th. I'll admit at this point with my fish continuing to seem healthy and happy and my numbers the exact same, I added 2 more Glo fish Tetras on September 2. Continue testing, some more water changes sprinkled in there and still the exact same numbers. On September 7 I took sample to the Aquarium store and had them test and they got the same numbers and said it of course had no cycled yet so add some more Activate which I did. All 4 fish continue to be healthy and seem active and happy. I had run across your blog
last week and ordered some Seachem Prime to try your method. Yesterday I tested and got all the same numbers. I have also started seeing some visible algae on the decorations so my friend recommend I clean it up since I have no algae helpers yet. So I cleaned some noticeable areas and did a 30% water change using the Prime for the first time, since I was about 1 in low on water from all the testing. I got busy cleaning the house and forgot to empty the test tubes immediately and came back to the about 6 hours later. The ammonia was definitely yellow no more doubt that it had any green tint. Not being a chemist I don't know if that would just happen to any ammonia reading OR if it was a more accurate reading. 24 hours later I just tested and got the same numbers but it does appear that the Nitrate reading comes quicker even though it's only 5.0. I've yet to have any Nitrite reading. Sorry so long winded but I wanted you to be able to have a full picture.

Hi Heather,

Unfortunately, cycling is something that takes weeks and to get a true picture of what is happening you should write down each days results and compare them. If your nitrates are going up, then they have to be coming from somewhere, and it could be that your tank is well on it’s way to being cycled.

Also, I wouldn’t trust any test reading that had been left to sit for 6 hours.

If Aqualife Activate acts similar to prime then it is possible that your test kit is giving a false positive for ammonia, including ammonium (harmless) in the total. As far as I know, Seachem is the only test kit manufacture that tests ammonium and ammonia separately.

Alternatively, you can use a free ammonia calculator like this one (NH3 is ammonium, NH4 is Ammonia) to see what is happening in your tank, However, you will need to know your tank temperature, pH and Salinity in addition to your ammonia measurement. While most saltwater tanks will know their salinity, most freshwater tanks won’t and you’ll need a device to measure this.

The alternative is to leave it a few days, see what happens to your nitrate levels. If you think your tank is cycled, you can skip the prime for 48 hours and re-test.

Thank you. I will get a Sea chem ammonia test kit. Because right now none of my numbers are changing. I know it can be a long process but as you can see I’ve never had a spike of numbers to even think anything is happening. I just feel at a loss. And nothing I read seems to match what I’ve seen happening.

If you have fish in your tank, then ammonia, nitrite or nitrate levels should all be increasing. Ammonia is given off when you feed your fish, when they poop etc, it’s unavoidable and at the very least you should be seeing a change in the ammonia reading after a few days.

That’s what I keep reading but here I am a month into it and nothing’s changed. I test every day. And it’s always the same.

Ok I’ve been dosing with Prime. I tested today and there was definitely no ammonia. Still never had any nitrites. Nitrate color looked paler orange today too. pH is 7.6 and HRpH is 7.4. Tank temp is 80F. Should I just keep dosing with Prime?

Hi Heather,

If you believe there is no ammonia, and no nitrites but your nitrate levels keep increasing, then your cycle is done.

Prime wears off 24-48 hours after each dose (assuming you dosed correctly as per volume of your tank) If you wanted, you can keep testing multiple times through this window and past it, to make sure everything looks okay.

Alternatively, keep dosing and monitor your nitrate levels. If they continue to rise but your ammonia and nitrate stay at zero then you can be confident your tank has been cycled.

Hi everyone,

I am new to the aquatic community and I have a 50g tank. I set up the tank 2 days ago and got eager and put some fish inside already. I currently have:
1 plecostomus
1 catfish
1 green tiger barb
2 stripped tiger barb
2 angel fish
2 snails (not mystery snails)
2 black cichlids (temporary)

When I bought everything from PetSmart, the lady failed to mention the nitrogen cycle, so I just put all of the fish in the tank with the water. Today, the tank was cloudy and according to the internet, that’s a bacteria blood, which is good I guess?
Anyway, I went to Petco this time and they were way more helpful.

I just would like to verify if what she said was correct.

The girl told me to remove 50% of the water and replace it with Seachem Prime treated water. Then test it with the API kit.
I just did a test now and the results are:
0.5ppm Ammonia
0.25ppm Nitrites
5ppm Nitrates

Where should I go from here? I only have a 5g bucket to treat and replace the water, so I’m not sure how to dose the Prime since it’s 5ml/50gallons. I have been using a bacteria supplement as well on the first day I received the tank. Should I continue to use the bacteria supplement for every water change?

Thanks everyone!

Hi Vanessa,

You can can work your way through the steps listed in this guide.

A 50% water change is going to take you 5 trips with that bucket. Once you get to tanks this size, I suggest using a water changer instead of siphoning into a bucket – it’s going to save you a lot of time and effort, depending on how far your tank is from the nearest water source.

On the prime question, .05 ml. use a measuring pipette, it will make it easier to precisely dose. Don’t worry if you add slightly more, an overdose shoudln’t harm your fish.

As for the bacterial supplement, there is debate as to their effectiveness. However, there is no reason not to continue with it. If it has been properly stored and within it’s expiry date, it won’t harm your tank.

Your tank is too small for the pleco! Pleco should be put in minimum 79 gallons for one. And they need to be several plecos, not only one, or it’s not a good life for a fish that likes to be in bank to be alone! So it’s not a wonder that you have nitrite & nitrate problems. For the other fishes, I don’t know, but try to get info, because for the pleco, you haven’t been given good advice.

Buy a bigger tank, or give your pleco. Plecos are not good fish to keep in a tank, they shouldn’t been bought, they require too many gallons and family members.

Doing 75% water change is too much, it’s very stressful for fish. It should be done in my opinion only if there’s a big problem with the quality of the water. Most of the bacteria are in the filter, that’s right, but you lower the number of bacteria when you do a water change, they are not all in the filter, there are also bacteria in your soil, and on every surface they can colonize, but a large part is often in the soil.

I set up a 75 gal fresh water tank late August. I’m cycling with fish in the tank. I have been testing my water every 2 or 3 days. I have never seen an increase in Ammonia, Nitrites or Nitrates. I was doing partial water changes but have stopped. Water chemistry continues to be good. My tank water has been some what cloudy and has not cleared as of yet. The fish are healthy and eating well. Please help if you can.

Hi Steve,

I would double check your test kit has not expired and isn’t faulty – ammonia won’t take long to build up to measurable levels.

If there is no ammonia or nitrites but nitrates, then your tank has cycled. Given that it has been over a month since you set up, this is another possibility.

Hi Ian, thanks for your reply. I checked my test kit and it is good until 2020. I’m using Tetra test strips and have also had the water tested at the local Pet Smart. I checked my water again today. No Ammonia, Nitrites or Nitrate. I’m really at a loss because this is not my first Aquarium. I had a 250 gallon Marine tank for several years and never had issues. I’m ready to go crazy.

Hi Steve,

Given you are not a beginner, I’m actually leaning towards thinking your tank is cycled and that something is depleting the nitrates. I mean, if there is one thing fish are good at, it’s producing ammonia.

No need to go crazy just yet. If you want peace of mind, I’d take a photo of your tank, write up your weekly ritual and list the equipment connected to your tank and post it to an online aquarium forum – it’s likely someone else has experienced the exact same problem as you before.

Hello again Ian, I appreciate your insight and comments. I’m not very tech savvy when it comes to posting on a forum. I am running 2 HOB Fluval 70’s as well as a Fluval 406 Canister filter. I believe your assessment that my tank has cycled is correct. Today I’m going to gravel vac which I haven’t done since I set up the tank
and perform a water change. I figure the worst that can happen is the cycle process starts over but I don’t believe it will. I will let you know in a few days the results, wish me luck!

Hi again Steve,

Hey, no need to doubt your abilities. If you can comment here, you are more than tech savvy enough to post on a forum!

Given that the vast majority of beneficial bacteria hides in your filter media, vacuuming the gravel and doing a water change shouldn’t have an effect if your tank is already cycled.

Also, that is a lot of filtration for a tank your size. Most would stop at just one of those filters. Not that this is a bad thing at all, more is always better.

I’ll be very interested to hear your results after performing maintenance.

Good luck!

Hello Ian, yes I definitely have a lot of filtration on my tank. I think it comes from when I had the 250 gallon marine tank for 15 years, it also had a lot of filtration. So I did a gravel vac and 75% water change. I tested the water this morning and chemistry is good, tank water looks much better. There was a lot of waste in the gravel that came out. I think I’m on the path finally and can enjoy the hobby again. I appreciate all your comments and help. It’s been a pleasure chatting with you, best wishes.

Hello, love this site, I now understand the cycling process!
However, please can I ask some advice?
I’ve had my 40l tropical tank for a few years but have never been successful in keeping fish alive in it ???? I decided that I have probably never properly cycled my tank and so thought I would start again and get it right this time. Twice the heater has overheated the tank and so I made the decision to get rid of it and go cold water with goldfish. I had kept the tank and filter running since the last of my fish died. The pet shop convinced me to get ‘temperate fish’ and so I came home with 4 platies and 2 snails. Then I did my research (yes I know now that I should have done this before getting the fish and am kicking myself that I could have cycled so easily with just food!).
I took your advice and got the testing kit you suggested. The fish were put in the tank 2 days ago and I have completed small water changes twice daily since. So I tested this evening (before my evening water change) and results were;
Ammonia 0
Nitrites 0
Nitrates 20
pH 8.2

Does this mean my tank is in fact cycled?
Also how do I bring the pH down?

Many thanks in anticipation of a response, any advice would be gratefully received.

Hi Laura,

Welcome back to the hobby! I hope you find more success this time round.

I would be hesitant to say that your tank has cycled after just two days. I would continue testing each day and perform water changes if your test results return a reading, for the next week.

As for pH, you can lower pH naturally with indian almond leaves or peat moss. Alternatively, you can use RO water however this will require you to remineralize it before adding it to your tank.

Hi Ian, I completed my gravel vac and water change, had quite a bit of waste in the gravel. Waited 1 day and tested the water, chemistry is good. The water still looks a bit cloudy and I’m wondering why. As you said there’s plenty of filtration so I would have expected it to be crystal clear. I’m still waiting for that to happen. If you have any thoughts about that I would like to hear what you think.

Hi Steve,

It’s possible that the pieces of debris that are floating around your water are so small, they are actually slipping through the gaps in your filter pads. This is an easy fix. Simply grab a super fine filter pad (50-100 Micron) like this one and place it after your coarser filter pad. It will trap the tiny particles that slip through and will return your water to a crystal clear state – it beats using chemical water clarifiers.

Also, if the bottom of your tank was particularly foul and kicked up a lot of gunk, you might need to give your filter pads a rinse in fresh water, to remove the excess sludge that has built up.

Hello Ian, thanks for the advice I didn’t even think about that. I’m going to pick up the filter pads today and I’ll reach out to you after the weekend and let you know the results. As always your comments are greatly appreciated.

Hi Ian, hope you had a great weekend! I think the tank looks a bit better today. This morning I removed the carbon from both the HOB Fluval 70’s and added more microfiber in its place since there is carbon in the Fluval 406 canister which I also put microfiber pads in on Friday. Maybe it’s going to take some time for the water to completely clear. I would like to send you a picture of the tank, maybe you may see something I’m not. Let me know if that’s possible and how to do that. Once again thanks and best wishes.

Hi Steve,

Thanks, I spent some much needed downtime with my fish!

Unfortunately I do not have the ability to receive photos through comments.

However, it will take some time for the filters to trap all the micro particles as long as you bought the right stuff, it will eventually all be trapped. The remaining gunk will settle on the bottom of your tank, ready for it to be siphoned away the next time you gravel vac.

The only other thing it could be is floating algae or bacteria, which will multiply in the tank but that’s a whole other ball game. From what you are saying, it sounds like small floating particles. Algae and bacteria have a much different look. You can see pictures of these in the cloudy aquarium water guide.

Hi Ian,

Most importantly, I want to thank you for taking the time to write this article! It is by far the best I’ve found on the topic. I had just a few questions I was hoping you could answer. I’ve scrolled through the comments and haven’t seen anyone ask these, but I apologize if I’ve missed something. I have a planted 20 gallon long tank whose cycle has crashed, and was wondering if I should continue dosing my liquid fertilizer weekly (I’m currently using API Leaf Zone, but I’m planning on getting Easy Green from aquarium co-op soon) or if I should wait until the tank is cycled again? Also, in regards to the 50% water changes when cycling with Seachem Prime, I assume that includes vacuuming the substrate and removing any dead leaves from plants? Lastly, I have approximately 2 inches of sand as my substrate. When I do a 50% water change, should I remove 10 gallons even though it will look like I’ve removed more than 50% of the water due to the substrate, or should I eyeball it? Thank you for your time, I greatly appreciate it!

Hi Madision,

I’m a little unsure on this one, I typically add plants after my tank is cycled, I have also never used API leaf zone and have little experience with it. You would be best suited reaching out to a planted tank forum ( is pretty great) and asking there. If it’s like other ferts, I wouldn’t have expected it to affect your cycle.

On the water change, it depends – in a properly stocked tank, vacuuming the gravel and maintaining plants can be done every 1-2 weeks depending on your schedule, I do it all at once with the weekly water change. Since you might be doing daily water changes in this cycle, there isn’t really a need to increase the frequency of these chores.

On the water change, eyeballing it is fine. It doesn’t matter if you take out more – the focus is on reacting according to your results. So if you fail to drop the ammonia or nitrite, a second water change may be required.

Hello Ian, I have looked at that site before and I have no doubt you are correct that there are small particles floating in the tank. The filter pads I purchased may not be the correct ones since the packaging didn’t say how many microns they are. I have ordered 100 micron pads from Amazon, just waiting for them. As always I appreciate your comments. I’m going to wait until I get the new pads, put them in and let the filters run for a couple of days before we talk again. Best wishes as always.

Thank you for all the great info! I have been following your steps after I made a mistake and messed my cycle up from setting up a new Hob filter and not Seeding it with bacteria from my old one. My readings today was 0ppm ammonia 0.25ppm nitrite and 0.5 nitrate. Do you beleave I am on the road to a cycled tank???

Hi Zach,

It depends, if it’s been over a week then sure. If this is your first day then something is amiss.

Hello Ian, Thank you , thank you, thank you! The filter pads came sooner than I expected as I have an Amazon fulfillment center near my home. I put the pads in all 3 filters on Thursday and did a 25% water change. By Saturday the tank looked great. I did change the pads Saturday in both the Fluval HOB 70’s as they were dirty and put clean ones in. I’m going to order some 50 micron pads just to see if they have more of an effect. As always thanks for your help, it’s been a pleasure talking with you. ????

Hi Steve,

I’m a little jealous of how close you are to an Amazon fulfillment center – my orders never come that quick.

That’s awesome. I’m so happy to hear it. Depending on how gunked up the pads are, you may be able to rinse them in fresh water to extend their use – since you are not worrying about beneficial bacteria in these pads, you can be pretty rough with your cleaning.

Here’s to your new crystal clear aquarium. Wishing you all the best in your future fishkeeping endeavors 🙂

Hi Ian,
I don’t see a lot of mention about “jump starting a tank” with Nitrifying bacteria. I have a 75 gallon Cichlid tank with 12 small Cichlids in it. I’m running a Fluval G6 and right before plugging in the pump, I put a whole bottle of One and Only Live Nitrifying Bacteria by Dr Tim. With 12 Ciclids and 2 Cory Cats, so far so good. Everyone is active, vibrant and eating. I monitor every day and only have trace NH3. I have been placing a packet of Marineland Bio-Spira bacteria in the tank every other day…right at the filter intake so it goes directly to the biomedia. I am a week into the cycle, no fish loss and clear water. I still have my UV filter off but my bio-filter and 2 power heads and multiple air stone decorations are going 24/7. Temp, GH, KH, pH are in normal range for Cichlids. I have done 2 15% water changes and using Prime on water change water and when I detect NH3. I check twice a day. My EC (electrical conductivity on the filter is reading ~900 which is high). Not sure why.
Any other comments?

Hi Michael,

You are definitely braver than me doing a fish-in cycle with that many fish.

The reason why I don’t really cover “jump starting” with bottled bacteria because it can be hit and miss as to whether or not it actually speeds up a cycle. I have some tanks cycle in under two weeks with it added as well as the opposite. I have also seen tanks cycle in under two weeks without it.

You have not listed your nitrite or nitrate readings. Nitrite is as dangerous as ammonia during cycling. Are you monitoring this too?

Hi Ian, it’s Steve again. Hope you are well since we haven’t talked in a while. My tank is doing great, fish are healthy and have not lost any. Water chemistry continues to be good with no problems. Tank water cleared up with the use of the 50 and 100 micron filter pads although it still looks a little cloudy to me.

I’m wondering if the Bio Max that’s used in the Fluval filters is putting some particles into the water? I’ve been thinking of using Bio Balls instead since they are plastic. I would appreciate your thoughts about that, thanks.

Hi again Steve,

I’m glad to hear your tank water has improved in clarity. Did you rinse your ceramic media before adding it to the tank? This will get rid of most of the lose dust and rubble that comes from the ceramic grinding against each other during manufacture and transport. I would be concerned if your biomedia is dissolving at such a rate it is putting noticable debris in the water.

I use sera siporax for my media and have not had an issue with clouding. I have also seen other tanks achieve crystal clear water while using cheap ceramic rings, so I don’t feel there is a need to swap over to a plastic biomedia, which IMO is inferior in terms of surface area for beneficial bacteria to live.

Also as an aside, how does the water look with different lighting? It’s possible your lights are making the water look cloudier than it is?

Hi Ian, thanks for your reply. I did rinse the bio media thoroughly before placing it in the filters. I asked the question because when I rinse the mechanical filtration at times I notice small white particles on the carbon bags that are under the bio media. As for the lighting I also thought that may be the cause but I
don’t believe it is because the water still looks slightly cloudy with it off.

Hi Ian, hope you’re having a great weekend. So guess what? I took 5 gallons of tank water and put it in a bucket. Then I rinsed the bio media from both the HOB Fluval 70’s in that bucket then put the bio media back in the filters. There was some small white particles that were in the water. Today the tank is clear and looks like it should. Tomorrow I’m going to do the same thing with the bio media in the Fluval canister. Even though I’m not a beginner as you know I’m still learning every day ????. Stay well and as always thanks for your help.

Hi Steve!

I’m doing well, thanks. I hope you are enjoying your weekend too!

That’s very interesting regarding the particles. Thanks for the update, I’m sure someone else will have the same “problem” in the future and I can now suggest this as a cause! Thanks for sharing 🙂

The article is really useful to explain the cycle, but seems an bit too much an ad for Seachem Prime to me… because dechlorinating the tank could be done for free! Just let the water 1 day or 2, that’s all! Boiling it or adding Oxygen could make the waiting time shorter. It’s ALWAYS better to do without shop chemicals if you can avoid them.

A good advice would be to test the tap water. Some people have no heavy metals and crap in their water, so the need of a water conditioner is…zero. While some people have toxic tap water, and they have to add a water conditioner.
Another advice: never trust the petshop sellers. If they are good sellers… they lie.

Hi Li,

Some interesting advice here, but I would suggest it’s aimed at people with experience in fishkeeping rather than beginners, who are the target audience of this cycling guide.

I don’t know about you, but I don’t think it’s particularly feasible. Boiling or storing 50+ gallons of water at a time and carrying it to your tank? It’s unrealistic. For beginners, using a dechlorinator is the easiest and most recommended option.

Same goes for your advice on testing tap water for heavy metals, most aquarium master test kits do not have the ability to test for these.

Finally, I agree that big box chains like petsmart and petco are hit and miss in terms of advice, generally leaning on the bad side. But small independently owned fish stores can be an amazing resourse, particuarly to someone starting out,

Seachem prime is my favorite dechlorinator due to how concentrated it is – it’s lasts longer than others. Also, since it can render nitrites and heavy metals harmless, it is useful in other emergencies. If you find another dechlorinator that works better, for a reasonable price and is commonly available for beginners, I’ll gladly swap out my recommendation.

But I do thank you for sharing your advice.

Hey Li, I read your comments about letting water sit or boiling it. You must have a very small aquarium if that’s what you’re doing. I have a 250 gallon Marine tank and when I do my water changes I’m removing a lot of water. It’s NOT feasible to boil 100 or 150 gallons of water. I really don’t think you know what you’re talking about!

Hi Ian, I just wanted to say hello and wish you a Merry Christmas and Happy New Year. You have been a big help and I feel as if I’ve known you for a long time. The aquarium and fish are doing well, as always thanks for everything.

Best Wishes

Haha, Hi Steve,

I’d say it’s still a little early for the seasons greetings – I still have not even gotten around to buying christmas presents or setting up a tree. But I appreciate it.

I’m super happy to hear that your fish are doing well. No need to thank me, I love to help others. Besides, you did all the hard work in figuring it out!

Wishing you all the best for the future!

Hi, I am doing a fish-in cycle right now with 5 Giant Danios and a 20 gallon tank. I tested positive for nitrites on Wednesday. I waited until Friday to do a water change because I did not have time to do it sooner, but I used Seachem Prime every day just to be safe. On Friday, I did a 40% water change using Seachem Prime again. Today, Saturday, I used the API Freshwater Master Kit to test my water levels. I came back with: (my temperature is at 75 degrees, by the way)

Ph: I’m not sure how to tell this one: I use the regular ph reagent and always come back with 7.6, the highest possible number. The kit said that if you get 7.6, to always try the high range reagent too to know the exact number, but when I use high range, I get 7.4, the lowest number. How do I know what my ph really is?

Ammonia: 0.25 ppm

Nitrite: 0.50 ppm

Nitrate: somewhere between 10-20 ppm

I didn’t think that my Ammonia, Nitrite, and Nitrate could possibly be that high since I had just done a water change the day before, so I’m not sure what’s wrong. What should I be doing at this stage?

Hi, it’s Taylor. I just commented about my 5 Giant Danios but I read the levels wrong.

Ammonia: 0.25 ppm

Ph: still same problem as last time

Nitrite: between 0.25-0.50 ppm, but on the lower side of that.

Nitrate: 5-10 ppm, but on the higher side of that.

Still wondering why they seem so high after I just did a water change, and not sure what to do next. Sorry for two different comments, my eyes are getting worse and worse!

Hi Taylor, it’s possible your tap water already has ammonia or nitrites in it. Have you tested your tap water to confirm?

On the ammonia front, seachem prime can cause a false positive for ammonia since the API tests measure both ammonia (dangerous) and ammonium (harmless) – when seachem prime binds ammonia, it is temporarily converted to ammonium. So while you may have a reading for it, it may not be as dangerous as you think. The only way to tell for sure is to purchase a seachem ammonia kit. Off the top of my head, this is the only aquarium test kit to test for ammonia and ammonium individually.

The nitrites are the case for concern and it’s not unusual for your nitrite levels to reach this high in a day if there is no beneficial bacteria there to “eat” them. You can either use prime or water changes to get it down.

Once those are under control, it’s a waiting game. Slowly you should see your nitrates increase as the nitrites get consumed.

Hi there,
We rescued a Betta with fin rot. In the early days, because his torn fins were so fragile, we kept him in his tank (about 2.7 gallons) without a filter (thought the current might affect them). He went through a course of antibiotics while doubtless killed ALL bacteria. After the course, his fins were still fragile and raggy, so we held off on the filter and did partial water changes daily. The ammonia remained at about 0.25 and zero nitrites and nitrates. We use Prime and API Quick Start.

Now happily, since his fins are growing in nicely, we got a new filter in for him. It’s been 2 days with the filter and the ammonia looks somewhere between 0.25 and 0.50 (so hard to tell with the thing) while nitrites and nitrates remain zero. Now I’m not sure how to proceed – at least some percentage of the tank water is still protected by Prime, while presumably some of the earlier Prime has already worn off.

We did 25% daily water changes because the presence of the ammonia upset us, but I think now that we should actually do them every 2 days instead to give the beneficial bacteria something to live on? So do we just start dosing with Prime for the ENTIRE water volume? How often should we do water changes during this cycling period, and how much? Help please!

Oh, and by “one dose” or “double dose” of Prime, do you mean one dose for the ENTIRE volume each day, or — in the case of “double dose”, two doses each day — say, one in the morning, one in the evening? Thanks so much.

Hi Catherine,

Thanks for being an awesome person and rescuing a Betta!

A double dose refers to doubling the amount required to treat all the water in your tank in a single time. Don’t spread it out over the day.

If nitrites are zero and nitrates zero (or low) then you are right at the start if the cycle.

As for water changes, the Seachem Prime is binding the ammonia, so as per instructions above, we try to keep it at 1ppm, and perform a water change when it hits 2 ppm (50% will cut this roughly in half to 1 ppm). And keep dosing.

How how often you change the water over is a judgement call according to your tank. You’ll need to base it off your own test readings.

You are dosing for the entire volume of water because your fish is constantly producing ammonia inside the tank, and it’s not a controlled amount.

Thanks a million!!

So we keep putting in new Prime every day right (at 24 hour intervals)? whether or not we do water changes? Is there a possibility of overdosing (I mean where there’s just “too much” Prime in that same body of water)?

On a side note, do you agree that Bettas *should* have a filter? Some people told us they didn’t need one; in fact the people we rescued him from were doing 100% water changes every 3 days….

P.S. I asked about the filter also because his fins are still growing back; he’s not 100% recovered yet. I imagine that would take at least a month more, but we didn’t think it would be good for him to go without a filter the entire time. Was this wise? Or should he perhaps wait till his fins are totally restored?

Thank you so much!

It doesn’t have to be right on the 24 hour interval, prime detoxifies for 24-48 hours. However, I would suggest doing it closer to the 24 hour mark than the 48 hour mark – you don’t want to let it get to a point where the prime has worn off.

Seachem themselves state that Prime can be dosed safely up to 5x, so if you are just doing a single or double dose, you won’t get close to the upper limit.

There is lots of back and forth on this. I’m of the opinion that every tank should have a filter. Especially for beginners – it just makes keeping water quality easier to balance.

100% water changes every three days, while harmless (assuming pH temp etc. kept in check), seems excessive. It was likely done to combat spiking parameters. You shouldn’t need to clean your tank this often. That said, a 2.7 gallon is right on the cusp of too small for a betta, I generally recommend a 5 gallon at minimum. Not only is there more room for a heater, filter etc, but the more water the easier the tank is to manage. Ideally you would want to get away with performing a water change every week or two (it soon becomes a chore) and a larger tank, correctly stocked, will allow you to achieve this. You should perform your water changes to your parameters – once your tank has fully cycled, and you see your nitrites getting excessive, it’s time to change the water. Whether that’s after 1 day or 1 week will entirely depend on a multitude of factors.

Betta hate water movement so regardless of his fin condition, you don’t want to generate too much current. A small sponge filter or careful positioning of a return flow can help keep water movement to a minimum.

I know this was somewhat disjointed, I’m currently on my phone. If you need further clarification, let me know!

Thank you SO much! We just gave him his dose of Prime for the day 🙂

We have another older tank (gups, corys) that I think is pretty much cycled — ammonia/nitrites down to zero and nitrate 10; at this point we can just keep to the routine partial 25% water changes once a week or so right?

Ought we to keep testing the water just to see when ammonia/nitrites reappear to get a better sense of how often we should be doing the changes? How often should we be testing for ammonia/nitrites in a cycled tank really?

Spot on, Catherine – your older tank is cycled so you don’t need to do this prime every day nonsense. You just perform water changes relative to the water quality. How much you change entirely depends on how quick your nitrates rise. 25-50% is the common rage of water changes that most people perform.

During cycling I recommend testing daily. This will allow you to quickly identify if something has gone wrong (say, you need a larger dose of prime to fix a nitrite spike) Testing is the only way to truly understand what is happening in your tank. If you skipped a day, and something went wrong, your fish will have to wait until the next testing day before you test and identify the problem – by then it may be too late for your fish.

It’s one of the reasons why I recommend liquid test kits over strips – it’s more cost effective, daily testing with strips can soon add up.

Yes, those strips are really unreliable I think. Do you know — the ones by Tetra — for the longest time they didn’t show up any nitrites or nitrates (for our gups at the time) and said our ph was way too low! It was only later with the liquid tests that we saw the nitrites/trates and learnt our ph was 7.6.

Oh by the way, I forgot to mention that in conjunction with the Prime, we had been using API Stress Coat to help with his fins. I think…… it …. helped… ? (“the healing power of aloe vera”!) Shall we continue dosing it with the Prime? And what about the Quick Start?

Another question — do you have any thoughts on marimo balls,the (ideally) genuine ones? We had one in the gup tank and I think that did help with the whole cycling thing. Now we’re wondering whether to add one into Betta’s tank — just a little uncertain whether that would be a good thing (in light of his fin issue). Thank you!!

Unfortunately, your experience with test strips mirrors that of many others, they are not accurate enough to rely on their results.

I have no experience mixing prime and stresscoat together, most people either use one or the other. I believe the only difference is that stress coat contains aloe, however it’s up for debate as to how effective aloe actually is. Prime also claims to stimulate the slime coat, so the theory goes you should be able to swap over to just prime without issue – it does more and is more concentrated.

Quickstart or any other bottled bacteria may or may not help speed up the tank cycle. In addition to the bottles containing different strains of bacteria, depending on the brand, they can also be dead on arrival. These bottles contain a living thing and if it’s no properly stored (too old, too hot or too cold), say it gets frozen in transit, then you are just adding dead bacteria to your tank. Unfortunately, there is no way to guarantee your bottle is alive. With or without bottled bacteria I have seen many tanks cycle both in under a week or over 2 months.

A marimo moss ball shouldn’t make a noticeable difference in an aquarium cycle. The “live” moss balls should be quarentined before being added to your tank though, they can introduce some unwanted stowaways.

Hi again Ian, more on our Betta saga 🙂
There isn’t any new ragginess on him thankfully, but we just did a water test and the results are curious — ammonia was 0.25 (with a hint of yellow) and nitrite was 0. So I was expecting nitrate to be 0 again, but now it’s definitely bordering on 5.0. What does it mean?

And p.s.– what would be a good length of time to quarantine a marimo ball? Thank you so much!

Hi Catherine,

That’s awesome news on the fin rot!

As for the nitrate, it can mean one of two things:

1. The second beneficial bacteria (nitrite ->nitrate) has appeared and is quickly converting nitrites to nitrate, so quick that it’s keeping your nitrite reading at zero. Sometimes this can happen before the first beneficial bacteria (ammonia ->nitrite) has established itself to the extent that it can process ammonia just as quickly.

2. Your tapwater actually contains nitrates. 5ppm is within the range that some water sources contain. You can eliminate this as a possibility by testing your tapwater prior to adding it to your tank. If your tap water contains elevated levels of nitrate then you will actually introduce this to your tank with each water change. You might want to take a reading of this 3 times over a week (say, Mon, Wed, Sun), just in case. Of course, by then your cycle will have progressed, but it’s always good to know the exact parameters of what you are adding to your tank.

Depending how paranoid you are, 2-3 weeks for quarantining.

Three weeks then haha

Hm ok I’ll test the tap for nitrate. Though it’s been zero for the longest time prior to this, so that would be interesting… I know the tap *does* have ammonia though :/

If it’s the first scenario, is that a good thing?

If it’s the first scenario, it suggests that your cycle is progressing as normal, which can only be a good thing 🙂

Sigh it looks like the second scenario — the tap water has nitrates at 5. What does this mean for Betta’s whole cycling thing and how should we proceed please?
Thank you so much.

I’d start by confirming that you are testing correctly.

Follow each instruction piece by piece to make sure you are not missing anything, and be generous when it asks you to shake.

Next, read your results under daylight. So go outside if you need to and look at the test. The lighting in your room can throw these off dramatically.

Now, you want to measure your:

How long it’s been since you started your fish-in cycle.
How long it’s been since your last water change
How often are you doing a water change

And list everything else you have in your tank, no matter how minor.

Once you have confirmed these basics are correctly listed, I can give you better advice on how to proceed.

Thanks Ian. Do you mean test the untreated tap? Or the treated tank water?

I’m pretty sure we’re doing the tests right and the treated tank water currently is ammonia 0.25ish (with hint of yellow), nitrite 0, nitrate 5, pH 7.2ish

The pure tap is ammonia 0.25, nit 0, nitrate 5, pH 7 (perhaps 6.8ish)

We don’t bother with temperature for our tanks anymore as we live on a tropical island and it’s perpetually between 25 and 30 deg c. We used to use a thermometer but it just sat there pretty much at 25.

> How long it’s been since you started your fish-in cycle.
Well as you know Betta was on the antibiotics and all that, so I’d say this whole trying to cycle him thing really started Dec 4th. He only has his sponge filter at present as his previous marimo was chucked and trying to keep things fairly pristine while he’s healing.

Okay, so if there is only a sponge in the tank, and recently, then this is the only place that bacteria can call home – so it was an essential addition.

So the ammonia in your tap + tank is 0.25. When was the last time you performed a water change?

I only ask because it shouldn’t take long (a few days) for your betta to increase the amount of ammonia in your tank. If you are doing your daily water changes like you suggested, then it’s all waiting game until you see nitrite increase.

Yikes on the spring water, it’s expensive enough to drink much less house a fish.

You know what I think accounts at least partly for the earlier zero nitrate readings was that he was still largely on spring water. The vet had suggested using that during his antibiotics course because of the ammonia in the tap water. When he finished his course, we started very gradually increasing the amount of tap water, and decreasing the spring, because really — spring is expensive!

Yes, the filter was definitely an essential addition. We’re hoping to get marimo back in (after the 3 week quarantine haha) The last time we performed a change was today; basically 25% every day because of the healing.

> Yikes on the spring water, it’s expensive enough to drink much less house a fish.
You bet. Hence the very gradual reverting to tap!

Do you think TWO partial changes a day — say morning and night — would be beneficial or unnecessary, in terms of his healing?

On the water changes, It would depend on how quickly ammonia, nitrite etc. rise. Ideally, there needs to be some of these chemicals in the tank for the beneficial bacteria to form. I’d perform water changes to your testing, rather than following a rule of two no matter what.

> I’d perform water changes to your testing, rather than following a rule

Yes, agree. Perhaps in addition to the routine morning testing during this healing time, we’ll test again at night, just to see where things stand at the end of the day, and take it from there. Thanks soo much again Ian — we’ll keep you updated (if you like haha); perhaps our experience will add to your arsenal of knowledge 🙂

That sounds like a great idea. I’d love to be updated, it will allow me to better help someone else in the same situation, should it arise! Thanks Catherine. I hope you have a merry Christmas if I don’t hear from you earlier.

Sorry Ian to be bothering you with yet another question. I was wondering (and please excuse my ignorance!) — if we dose 100% daily with Prime, does that bind up the ammonia/nitrite such that there isn’t any for the beneficial bacteria to “eat” and “grow on”?

With our older gup tank, I think it got cycled (with the fish in) through our almost daily 25% water changes, dosing only the fresh 25% volume of water with Prime and Quick Start each time. We tested every day till it got to the levels they are now. Could I please ask in what ways is that method inferior to yours? Sorry, I definitely don’t mean to imply that you method might in any way be “inferior”! I just really want to understand how it all works! Thank you so much!

All good Catherine, I created this site to help others to the best of my abilities 🙂

Nope, these chemicals are still able to be chowed down on by bacteria, even if treated with prime. If you experience an ammonia spike in a cycled tank, part of the reason we treat with prime is to give the bacteria a chance to catch up while keeping it harmless to fish.

If you google, there are hundreds of different ways to cycle your tank. None are inherently wrong. In the same light, no-one could argue that their method is superior either – if you reach a cycled tank using a method that was easy for you, and achieved the same result, then that was the best way for you to do it.

With that said, I do not have the opinion that your method is perfectly repeatable. Only treating the 25% may not work if you have fish with a high bioload (say a messy eater or one that poops a lot). In this instance, more ammonia may be produced than you have dosed for. That’s not to say that what you did was wrong, it worked for you and that’s fantastic.

This method is what works best for me. I find it to be repeatable, regardless of what goes in the tank. This is good for beginners, as it helps to narrow down things that can go wrong. If followed correctly, it also allows me to more easily advise as to why something has gone wrong, in the worst case, since I am very familiar with the entire process, since it’s the one I have personally used.

Also, no need to apologize – questioning and challenging is how we learn. Heck, if I don’t have the answer than I’ll go and find it for myself, so I learn too! After 30 years fishkeeping, there are still things I learn – Just last week was the first time I had to treat a case of anchor worms. Definitely not something I knew how to treat off the top of my head.

I guess what I am trying to say, in a rambling way, don’t stop asking questions 🙂

Thank you SO much Ian!

We’re pressing on with the cycling — ammonia still at the same 0.25ish level and zero nitrites/trate. Perhaps one Betta takes a little longer to get things going compared to a little family of gups and cories.

We will perhaps try the marimo — after quarantining it for 2 weeks haha

Thank you so much again; I truly appreciate your time and patience <3

Hi Catherine,

The worst thing about cycling is that it takes time. When comparing day-to-day,the process seems frustratingly slow. I highly recommend recording your daily measurements, so that you can see that progress is indeed being made. If you have excel skills, you can create a line graph to help visualize the progress. The big thing here is patience.

My only suggestion would be to grab a filter, if you have not already. A small sponge filter will do – it will give a good place for your beneficial bacteria to build themselves a moveable home (you can transfer it to another tank to make cycling much quicker if you need to etc.) I prefer the “hydro sponge” brand but in all honesty, anything will do.

Oh Ian, we’re so sad to observe that Betta is just now showing some new ragginess/loss on a bit of his tail when we did his water test today.

Ammonia is still 0.25ish and zero nitrite. As previously mentioned, we had been doing partial water changes every day prior to introducing his new filter 5 some days ago, adding Prime for just the new water with each change. Since starting this cycling was the first time we stopped doing it every day.

His tail had been growing back nicely, slowly but surely, and today this — not sure what to do/what it means :((

Oh yes, we are recording every day and yes, he does have a small sponge filter. It has a similar structure to the Hydro-sponge I believe, but we put a few gravel pebbles in the upright tube thing (out of which the bubbles come) to baffle the outflow/turbulence a bit. Is that bad?

A better way of doing it would be to add a bleed valve to your air pump line, (a connector piece + a flow control valve) this will allow you to control the air flow without blocking off the sponge filter. Open the valve wider to reduce the current. This will keep the current that flows through the sponge constant, rather than potentially blocking off areas.

Regardless of progress, a fish-in cycle is tough, especially on a fish that is already sick. There is never a guarantee that your fish will survive, regardless of how you cycle. It’s possible the cycle and other stressors are responsible for the new rotting areas, assuming you have confirmed the fin-rot isn’t a secondary symptom of another disease, either bacterial or fungal. It is also possible that the fish has non-noticable symptoms of other diseases or even parasites that are stressing it out, and despite your best efforts, it was too far gone from it’s previous home to be saved. Unfortunately, sometimes these things are out of our hands.

The best solution would be to move it to a tank that is already cycled water quality often plays a huge part in how quickly fin rot progresses and in a non-cycled tank, it can get dicey. Do you know anyone who has a hospital tank you can use in a pinch?

Oh, I just saw the last part of your reply (odd; how did I miss it haha) — “The best solution would be to move it to a tank that is already cycled”…

Well of course our other tank is cycled, but I don’t want to imagine Betta and Gup together haha… We do have an extra smaller tank, about 1.5 gallons.

Thank you so much Ian. We will keep hopeful and doing our best for him! He is very sweet — we will update you in a few weeks on his recovery 😀

Have a wonderful Christmas season and thank you so much again for all your help!!

If the extra small tank is cycled, It could potentially be a viable solution, even though it is certainly too small, I would strongly consider the tradeoff vs pristine water. Unfortunately, this is a judgment call that only you can make. Whether you do or not, you are not wrong. You are just doing what you believe is best. This would also free you up to fishless cycle your current tank, which is much easier. Of course this advice is all for nought if the tank isn’t cycled. Some independent pet stores sell pre-cycled sponge filters, which can reduce a cycle down to near instant (up to a couple of days), but these stores are few and far between. Just listing ideas as they pop in my head.

Otherwise, just keep doing what you think best. It’s clear you have your head around testing and cycling, so if you feel it’s better to mix things up then go for it. My advice in this guide is for beginners who are not cycling with an already sick fish, so if you have a better solution, roll with it.

I hope you have a merry christmas and, if I don’t hear from you before then, a happy new year. All the best and I’m sending your betta my well wishes!

Thank you so much Ian. Nah, the smaller tank definitely isn’t cycled — it’s empty and dry on a shelf! Betta’s adoption was unexpected — he had been dumped at our vet’s where we were actually with our dog that day.

I think we might have to cycle his tank the way we’d done with Gup’s — the daily small changes — because I’m presuming in his healing state he’s just very sensitive to any ammonia or whatever. Gup’s tank was helped by the presence of an active filter the whole time (and possibly the marimo) so now hopefully the presence of the new filter in Betta’s tank will help things a bit. It’s not as “powerful” a filter as Gup’s, so we’ll see. Fingers crossed!!

You are an angel for grabbing the Betta and attempting to give it a better life!

It sounds like a good plan. I can’t fault it. Please keep me updated with how it all goes, or if you have any more questions, drop me a line! All the best!

Hi Ian! Hope you’re enjoying the holidays!
I was wondering — how often should one give the whole tank a wipe-down, including the floor? To do that would of course necessitate removing everything in the tank, including fishy, which as I understand it, we shouldn’t do too often?

I don’t mean really obvious scum and algae. But some time back, I noticed a sort of clear, but shiny/slimy quality to Betta’s floor, so decided to clean it. Sure enough, it felt slimy, but came off easily and still hasn’t returned since. It was on the walls to some extent as well, but not really much. I figure it’s some sort of scum thing that naturally forms after awhile in a wet environment, like on bath tiles, so was wondering how often/imperative it is that I clean this stuff off. Thank you!!
p.s. You may be interested to know that Betta’s tank is finally showing a bit of nitrite!

Hi Catherine,

There isn’t really a hard and fast answer here, some people wipe down the walls every time they water change, others only wipe down when their view starts to become obstructed by scum and algae. As long as your water parameters are normal, you can do it as often as you need.

As for the gravel, I suggest grabbing a gravel vac, this device will clean your gravel as you change the water at the same time. I consider it an essential product as poop and uneaten food can fall into gaps in the substrate and turn foul. If you want a good one, check out my reviews section, I have personally tested over 40 different types and stand by my recommendations.

Both of these can be done with fishy in the tank.

It sounds like you might have been dealing with diatoms (brown algae) these are common in new tanks and often go away on their own.

Also, that’s awesome to hear about your progress!

Unfortunately, while I can combine comments, I can’t move them outside of their replies, the software I use does not have that functionality. You’ll need to create a new comment.

Thanks so much Ian!
How often do you clean the gravel? With every water change or once a month or..? We’ve heard lots of conflicting views on this!

I personally do it with every water change. A gravel vac siphons water so you might as well give your gravel a suck while you are at it. It’s not even an extra step. Depending on your bioload, how much you feed etc you don’t have to clean your whole gravel. If you do weekly for instance, you can do half one week and half another. It’s another one of those things were you “do what works for you and your schedule” I mean, if you don’t have the patience to do it every week then once a month is much better than going months without doing it. As always, testing your water parameters will clue you in as to whether you should be doing it more often.

At first, you’ll likely struggle to clean your entire tank with a single water change anyway. These things take practice but eventually you’ll be gravel vaccing like a pro.

Hi Ian! Quick question please! We’ve never had a sponge filter before (ours is similar in concept to the Hydro one you mentioned); how do we clean it? Betta’s filter is one month old today and I think we have to clean in? As you know we’ve been trying to grow a friendly bacteria family on it haha.. So today it’s a month old but doesn’t look gunky or anything; just feel we need to clean it on principle? (we clean our Gup’s filter once every couple of weeks and theirs *does* look gunky). Do we have to pull off the sponge or something? Scrub the tube? We needn’t be too vehement about it all, right?

If your tank has cycled, then cleaning is simple:

Grab a bag (I use those ones that your fish come home in from the petshop) and fill it with enough tank water to cover your sponge filter plus a little more. Squeeze the sponge filter and work at the surface with your thumbs, rubbing to remove trapped detritus. Empty the bag, refill and repeat. 2-3 times will do it.

It doesn’t matter if water that comes out is still slightly brown or your sponge filter is discolored. You just want to remove the stuff that is clogging it.

If it doesn’t look gunky yet or your tank isn’t cycled yet, you can hold off. This filter isn’t so much providing mechanical filtration to your tank as it is biological filtration – in part thanks to the reduced flow. So, it shouldn’t gunk up as quick as your other filter.

Thanks so much Ian! No, it doesn’t look gunky AND his tank *still* isn’t cycled (ammonia and nitrite just hovering at 0.25; don’t even bother with the nitrate for now); we’re already accepting that his will take awhile because of the daily water changes. So we shan’t clean today — I guess just wait till his tank is cycled and/or the filter looks gunky?

Spot on. For now, you don’t want to do anything to disturb the colony of bacteria. You want that stuff to accumulate. I’m glad to hear you are being patient with the process 🙂

Hi Ian! Not quite related, but have you ever heard of/used Boyd Enterprises Freshwater Vitachem? Thoughts?

No personal experience, but I have spoken to people use it as a “daily supplement” and claim their fish are happier because of it. Anecdotal of course. Me, I’m dubious of anything that claims to be a “complete vitamin supplement” given there are thousands of different species of fish, with very different needs. I mean it’s benefits, such as fish coloration are better achieved though proper diet rather than feeding poor quality food and using this for color. All-in-one products generally have more marketing appeal than they do practical use. The problem with many of these products is that they are not used in isolation of other solutions, and I have often seen benefits miss-attributed to the product instead of the additional measures taken, such as improving water quality and an improved maintenance routine. I assume you want it for the claims of fin regrowth? Checking out the ingredients, studies suggest the included amino acids help promote overall growth of fish in aquaculture (add weight) I’m not sure where the claims of fin-regrowth come from. I couldn’t find any studies referencing any ingredient in particular relating to fin regrowth in isolation.

Thanks so much Ian. Yes, it was mentioned (anecdotally) by a friend who felt it really helped her Betta’s fin regrowth. Of course she was doing the water changes too, so… I guess it doesn’t hurt. Someone else mentioned Seachem’s Stress Guard, which I do set more store by. I read somewhere once that their fin regrowth is sometimes like a “one step forward, two steps back” affair, and I think it’s sort of true. The past couple of weeks he had no new ragginess — the longest he’s gone — and then this morning he did, which we can only attribute to our water changing a slightly lower percentage the past couple of days (ammonia’s at 0.25). So it seems like we MUST keep to the 25% we’d been doing previously.

Oh these things definitely take time. If you are seeing noticeable improvement with your current routine, albeit slow progress, I’d just keep doing what you are doing. I get the appeal of looking for that “silver bullet” but I think even if these extras were to help, the whole progress will still be a test of patience – your fish is essentially regrowing a piece of it’s body. That’s a huge process in itself. Every instance I have seen of fin regrowth, except in really minor cases, has taken months. While YMMV, the big thing to remember here is that it’s going to take time and patience.

Hi Ian! Happy new year!
I thought I’d write up a little “report” for you on the “cycling-tank-with-delicate-fin-rot-recovering-patient” before I forget haha…

So as I’d mentioned previously, nitrites finally entered the equation; for the past few days, levels have pretty much remained at ammonia – zero with hint of green; nitrite at 0.25 vaguely bordering on 0.5; and nitrate 10ish. After much thought, we had decided to sort of combine your method with ours – i.e. dosing with Prime, plus partial water changes, every day.

Now prior to all this cycling stuff, when he had been on antibiotics, we had been doing partial 25% water changes for him twice a day, as somehow once didn’t seem enough (fins would show bits of new ragginess). So we carried on doing the two changes plus the dosing. But after awhile, I thought since we’re also dosing every day with Prime, why do we need to do two? One should be enough and would get the cycling going faster right?

Well here’s the interesting thing. I’ve observed that he would be carrying along healing fine for so long as we did the two changes. But the moment we switched to one, he would show bits of new ragginess the next day. And so it seems we are compelled to keep to the two changes plus the daily dosing until he is completely healed (still have about half an inch worth of fin to go) or at least until the tank is cycled.

Which made me start questioning why, despite the daily Prime, this was happening. I can only conclude that 1) his fins, the new regrowth, are just still in a very delicate state and highly sensitive/reactive to *any* toxins and 2) the effects of Prime may actually start wearing off even before the 24 hour mark.

So that’s the report to date. What do you think? We’re also wondering when we should clean his filter, which you know is only about 2 weeks’ old. Part of me feels like it needs a bit of rinse (not because it looks gunky, but just.. because) and part of me feels like we should let it continue sitting for another week or so to pick up more good bacteria. Thoughts? 🙂

Happy New Year!

Thanks for the fascinating read Catherine. That’s great that you identified a technique that is working for you!

I’d be leaning towards the sensitivity as it is generally accepted that pristine water is a major contributor to how well fish heal. If prime wore off before the 24 hour period, it would be very well documented by now, it’s a very commonly used product by beginners and experts alike.

If I was in your shoes, I would keep what you are doing and see if you can reduce water changes once the tank has cycled.

As for the filter, what filter are you using? I tried looking through the comments but I don’t think this was clarified, that or my old eyes missed it.

Haha… it’s sponge remember 🙂 I’d mentioned how we put a few gravel bits in the tube to baffle the current a little. It has to be sponge I think, as he’s a Betta and you know how they are!

Thanks for Clarifying, I answer so many comments from different people that I often get mixed up, especially with ongoing exchanges. For a sponge, unless it looks super gunky, I wouldn’t touch it until after the cycle is over. After this 2-4 weeks with your water change isn’t a bad routine. Some people buy those stackable sponge filters and wash one sponge one week and the other the next. It all comes down to your routine and what you find easiest.

Thanks SO much Ian!
By the way, does 0 ammonia ever look truly yellow? Like um…a yellow raincoat? Or, to put it another way, does a vague hint of green signify that we’re still not there yet?

Aw thanks. Zero does look distinctly yellow…pee-ish really haha… OK we’ll keep aiming for that. When the tank is cycled, it should stay consistently that right? Even after say a week, when it’s time for a partial water change?

Yup, your ammonia should stay at zero once your tank is fully cycled. To put it simply, the beneficial bacteria should eat this and nitrites as quickly as they are produced. So quick, in fact, that they won’t show in your test. Any measurable parameters here will clue in that something is amiss. The only parameter of the three that should steadily increase is nitrates, that are then reduced through the water change.

Hello Lan,
I have been doing a fish-in-cycle for about two weeks now using prime.
The Ammonia hasn’t gone over 0.50 ppm. I have a betta in a heated and filtered 5 gal tank.

The problem I have found is that it is starting to look like my fish is getting fin rot.
Yesterday I did a 50% water change to see if that could help?

How should I go about dealing with fin rot while doing a fish-in-cycle?

Thank you,

Hi Kim,

There was another commenter further down, Catherine, who experienced the same – dealing with fin rot for her betta while cycling. She found success with daily water changes along with following this guide. You could read through that exchange for more info. It’s a tricky one since for fin rot, you want to keep the water as pristine as possible, but to cycle, there also needs to be a degree of ammonia.

Hi Ian,

I’m a beginner aquarist and was impatient. I have a 10 gallon with some small fish in it/ I’ve been charting daily water tests multiple times a day to see how things are going. I’ve been doing some water changes and using Seachem Stability and Prime to help with the nitrogen cycle.
I think because I’ve been adding stability my cycle is a little wonky. I’m nearing the end of week 2 and my current numbers are Ammonia at 2.0, nitrite at around .5 and nitrate at around 10. So far, everyone is alive and some of the fish even had babies. I’ve been making upogrades to the tank as I can (better power filter and lighting for the live plants). I’ve been doing a lot of research and am just not sure about water changes at this point. I was steady on Ammonia levels at about 1.0 since Jan 8 and now i’m seeing an increase. I’m feeling like I should do a water change to clear it. I just a water change 2 days ago when I hit 2.0.
After reading your website, I added a bit more prime to cover the combited ammonia and nitrite levels. Any suggestions on what to do? Water change? Keep testing and adding prime? cross my fingers and pray to the aquarium gods?

Thanks so much,

Hi Christina,

When you changed the filter, you might have caused your cycle to restart (did you keep the old filter running, add filter media to your new filter or remove it completely?) It’s possible this is the cause for the raising ammonia levels.

Even so, the fact you see nitrite and nitrate is promising. You can either use prime or water changes to keep ammonia down, or even both. And yeah, when we do a fish-in cycle, we all pray to the aquarium gods, because even if we do everything perfect, there is still a chance the fish won’t make it. It’s a depressing part of the hobby.

Id personally do a 50% water change, to get your nitrate back down from 5 ppm, and keep monitoring from there, either using prime or a water change to keep things low.

Based on what you are saying, besides the setback, everything seems to be progressing as usual.


I changed the filter pretty early in the process. I changed the filter about 3 days after adding fish. I started the stability the day before I changed the filter so I figured since it was so early I wouldn’t lose much.

So in the last five days, I did one water change, about 30-40% with no change in nitrates. It’s been pretty constant at about 10 since I started recording numbers on paper which was on 1/6. I’m using the API test tubes but sometimes I find determining the colors to be tricky. I always read the test tubes in the same place under the same light. Any suggestions on reading the test tubes?

I just did about a 40% water change about 40 minutes ago. Filter is running on full speed to help circulate the water. I added a dose of stability and prime in with water change to make up for the fact. I also tried to really hose up some of the left over food. I think part of the reason is I was experimenting with tablets. I have one bottom feeder (kuhli loach) and I wanted to make sure it was eating too. I’ve been trying to be really conscious about how much food the fish get and when i feed them. I can’t wait till this process is over. This is harder than taking care of my cats!


For the test tubes, read them outside in daylight, unless you are using daylight light bulbs, (around 5500k) which are not common in homes, you’ll see inaccurate colors. Natural light is best for color matching.

So, on your nitrates, it doesn’t mean your nitrates are at 10, it means they are between 10 and 16 (after this you would probably match it with 20). So if you do a water change and your nitrates are at say 15ppm, a 30% water change would get it down to 10ppm, which is why you won’t see a change. This is worsened once you get to the 40-80 or 80-160 range. So once nitrate levels get up there, I suggest water changes to bring them down, so you can see the rate at which they are increasing. Also, I’d suggest testing your tap water, prior to adding it, so that you can see if there is a default level of any parameter there. It’s not uncommon for tapwater to have detectable nitrate levels. This all just paints a complete picture.

In all honesty, it sounds like everything is progressing as normal. It’s frustrating and you may find you have another 2 weeks or even longer before it looks like it’s wrapping up. But after that, it’s smooth sailing!

Also, I get what you mean with your cats! It’s funny how lots of parents get “fish” as a first pet for their kids, to show that they are ready for pet ownership – fish are a lot harder to keep alive than a dog or cat in the way that you don’t need to know chemistry for these four legged pets – can you imagine explaining cycling a tank to an 8 year old?

Thanks so much, Ian.

Before I found your site, I had ordered a free ammonia vs a total ammonia test from seachem. It came last night and I ran the test. If I read the test correctly, I have little to no (>.02 ppm) of free ammonia. Total ammonia was off the chart. So I figure I’m doing pretty good with the cycle like you said. At this point it’s just trying to keep these nitrates down. My nitrites haven’t fully colonize. When I do a water change, I see the nitrites showing the most change.

So far still have all my fish!

Thanks again,

Hi Christina,

That’s fantastic to hear. It sounds like everything is progressing smoothly. Unfortunately, it’s a process that just takes time. Hang in there, it’ll be worth it in the long run!

Hi Ian! I have a slightly weird question today, so please bear with me! You know how we’re doing the “daily water changes while cycling because of the Betta healing thing” right? Well, I’m wondering – in our case – when ammonia and nitrite are zero, does that mean the tank’s successfully cycled?

I mean, I know in “regular” tanks that means they’re cycled, but in our case, the water’s being changed every day – it’s about as pristine as it could get. At this point, ammonia’s finally down to zero and nitrite is a very light 0.25 (ammonia was at 0.25 for the longest time and nitrite 0.25 to 0.5).

So I’m wondering, when both are down to zero, is the tank truly cycled? Or do our daily water changes somehow give a…“false positive”? In our cycled tank for instance, we change the water weekly – we KNOW (and sometimes test, just to be sure) that ammonia and nitrites are always zero; only the nitrates go up some. But in this tank, when the ammonia and nitrites are zero, if we were to say, not change the water daily anymore, would the ammon and nitrite suddenly reappear? In which case, it would mean the tank *wasn’t* truly cycled right? And in which case how would we know when it was??

Sorry, I know it’s rather a weird, convoluted question! Hope you get what I mean ^o^’

For you, it’s a weird one. If you are keeping ammonia at 0.25 then that’s the amount of ammonia that your beneficial bacteria will be able to break down. So while your tank may technically be cycled, it may only be able to break down 0.25 of ammonia within a set period as the beneficial bacteria hasn’t grown in number to break down more – beneficial bacteria adapts to the amount produced, that’s why in a fishless cycle we aim for 4 ppm of ammonia.

So yes, your tank is cycled once these reach zero, but there is no guarantee it will be able to go a week without a water change, as a normal tank would. Once your fish is healed, and you slow down on the water changes, it’s possible you’ll see an ammonia or nitrite spike. If this is the case, just proceed with a fish-in cycle in the usual way.

Yes agree, thank you so much! I guess once he’s completely healed, we’ll slow down the water changes very gradually and monitor. Possibly theoretically the beneficial bacteria would also be very very slowly growing in the meantime and can deal with the eventual (gradual) slow down in the water changes? I remember when we were cycling the gup tank way back when, ammonia and nitrite never went beyond 0.5 either (hmph, looking at the test results online now, it looks like our ammonia was more like 0.5 than the 0.25 we always thought). At that time we just dealt with it with daily water changes and eventually it successfully cycled.

If you slow down the water changes then the beneficial bacteria will absolutely gradually grow in number to adapt to the increase in ammonia produced. It may be a balancing act though, lucky you have gotten good at your testing during this period! I’ll bet you’ll be glad when this ordeal is over!

Oh you bet!! Not that we ever regret adopting him — he’s so cute lol. I’m thinking once his fins have fully regenerated, we’ll still keep up the daily changes for some time, but decreasing the amount very gradually by say 5% every few days..or something like that. And then when we see that ammon and nitrites manage to consistently keep to zero, we’ll gradually increase the spaces between changes, say alternate days, then every 2 days and so forth. Sound sensible?

It sounds sensible, except rather than stick to a routine,such as strict water changes every 2nd day, I would suggest going off what the water parameters say. But even so, if all goes well, you should definitely be able to follow a routine that is similar to that in the least.

Thanks Ian! I’ll write a report in a bit 😉

P.S. I was wondering, how often should we take out and clean aquarium decorations? They don’t look gunky at all and we hardly ever do lol.. And then when we do, we’re very “tender” about it, as we envision entire families of beneficial bacteria growing on them! Please advise how often and how we ought to do it really!

It all depends on the rest of your maintenance routine. If you are performing water changes, regularly vacuum your tank, and keep an eye on water parameters, then rarely. If you are my niece, who hates the little maintenance she already has to do, then never. Both of these are fine. Because of how decorations are sealed, there isn’t a whole lot of surface area for beneficial bacteria to cling to so cleaning them won’t have any real impact on the balance of your tank. The filter should be the primary home – allowing you to remove bits and pieces and rearranging your tank as you choose without crashing your cycle. The only reason you would ever clean them is if they begin to lose their sheen/detail due to grime and gunk eventually clinging to them and that’s a personal choice. I actually don’t mind how decorations appear to “age” as the tank progresses, but that’s my opinion. Everyone is different and that’s cool too. I guess what I’m trying to say in a rambling way is that it’s up to you.

Hi Ian,
I have another slightly weird question today (and please feel free redirect me and post this to a more appropriate post if you have one) — we were wondering if gravel should always remain wet and in the tank, from the standpoint of the beneficial bacteria of course. That is, is it bad if the gravel is ever taken out of the tank to be washed for instance? How long does the bacteria survive out of the tank? Thank you!!

Hi Catherine,

Admittedly, this ones a bit more out of my expertise as people don’t really take gravel out of their tank with the goal of keeping the beneficial bacteria alive, not unless it’s being transported in which case it will be sitting in tank water anyway. If you are feeding correctly and regularly gravel vaccing, the gravel in your tank should hardly gunk up at all. A little gunk is okay – a fish tank is not a pristine environment. Your fish live in “gunky water.” It’s kinda their thing. I don’t think I have come across a fishkeeper who includes washing gravel as part of his weekly routine.

If you are exceptionally concerned, clean half at a time. By clean I mean take it out and swirl it in tank water, rubbing lightly at stubborn bits. Next week clean the remaining half.

And again, while some of the beneficial bacteria can be found in your substrate, most of it is in the filter. This is why adding gravel substrate to speed up a cycle is generally slower than adding a pre-cycled filter.

Oh dear. We were given a Water Garden for Christmas and set it up according to the instructions. One Betta fish, 3 gallon tank. It never mentioned anything about the nitrogen cycle. The first fish died the next day. I cleaned everything and acclimated the next Betta. (Following better instructions than came with the kit) Do you happen to know if growing plants affects this cycle? I’m about to make this an experiment for my son. I’ve been googling all day, trying to figure out if the current is too strong, whether his fins should be fluttering all the time, you name it. Don’t really want to kill this one!

Hi Angelica,

Unfortunately, the aquarium cycle is a beginner trap – that is often missed. Don’t worry, you are not alone here.

Growing plants won’t have noticeable any impact on the speed that the tank cycles. Betta come from calm almost still water, if the water current is strong, it will stress your betta which will lead sickness or even death. I cannot sayt how much current your water garden creates.

I’m bookmarking your site; it’s been the most helpful in my frantic googling. The filter I’ve put all the way to the floor to avoid sucking up the fish and the output is already softened by a plastic sponge. The fish is floating just fine and slept on the gravel without tucking himself anywhere. I’m going to see if there is a sponge that would fit over it when I go to the pet store today to pick up a test kit and hopefully some prime and a siphon. I no longer trust the kit. I honestly think we may have picked a sick fish from the start. This one is much more active and inquisitive. He may have fin rot, but I’m hoping that maybe it’s just fins burned from ammonia? Is that a thing? This kit is now just a 3 gallon tank with a lid I happen to grow things on.

Hi Angelica,

Fin rot can be caused by many things, bad water parameters being one of them. cycling your tank and doing regular water changes/tank maintenance will go a long way in preventing this. Fortunately, fin rot is very reversible. And yes, it certainly is possible you picked up a sick fish from the start, if it was a betta, these can be kept in some really poor conditions prior to being purchased.

Hi Ian. I am currently into a 2wk fish in cycle and I have 1 goldfish that was burned very badly by the ammonia. I do not have a quartine tank set up and he looks like he may have a secondary infection. I did order a filter from angel fish and expecting its arrival today however I am not sure what to do with this one poor fish. Can you help?

Hi Elizabeth,

If your fish is suffering, you’ll need to try continue the cycle while keeping the water as pristine as possible. Depending on what the secondary infection is, you may need a specific medication. To give your fish the best chance of survival, you’ll want to keep ammonia and nitrite as low as possible. This will likely require daily water changes. Check with your test kit and take action as needed. Unfortunately, there is no guarantee your fish will survive this, but it will give it the best chance.

Hi Ian!
Brace yourself for another slightly weird question. I was wondering, couldn’t we fishless-cycle a separate tank while Betta is recuperating, then transfer him to it when he’s fine?

Also another weird question — is it a nasty/unwise/ridiculous idea to save Gup’s used filter sponge to “seed” Betta’s tank? Gup’s tank has a “traditional” filter, with layers of spongey (and stony) filter media within a plastic casing; sometimes one of the sponges deteriorates to the point where we have to replace it with a new one. We actually sit that old sponge with the new one for some days to seed it a bit, which led me to wonder if we could “share” it with Betta haha… Thoughts?

Hi Catherine,

Not weird at all. I would think that your fish-in cycle would have completed by the time your fishless cycle neared the end though. If you do go down this route, don’t forget to acclimatize him when you transfer him

If the filter has not been removed then it could contain some beneficial bacteria. How much will depend on how far along your cycle has progressed. If it’s fully loaded with the stuff, it could speed up the cycle of your new tank. Otherwise you may not find it noticeably makes a difference. I’d try either DR Tim’s one and only or Tetra Quickstart (both are the same strain of bacteria) in addition to this.

Thanks Ian!
Yes. the filter isn’t removed. Gup’s tank is cycled, so that’s why I thought their old sponge must have a fair bit of stuff. But is it “unhygienic” to share it with Betta?

On another note, what would account for an occasional re-appearance of ammonia in a cycled tank? About 0.25, which goes back down to 0 after a water change or two?

Unless your tank has a disease outbreak or similar, there isn’t anything wrong with sharing a filter. It’s how plenty of newbies kickstart their cycle.

Such a small amount of ammonia? I’d monitor what happens prior to it’s appearance. feeding time? three days before water change day? Etc. It’s possible your tank isn’t fully cycled in relation to the bioload yet. It’s honestly hard to say without backtracking what happened prior to measuring it.

Thanks so much Ian.

Yes, just a hint of it. And yes, it does sort of tie in to feeding time sometimes I think… how long a gap should there be between feeding and testing?

I think the tank is fully cycled though? as the weeks between such occasions are fine.

Try giving it an hour or two after feeding and see what the results are. It’s possible the proteins in the food are rapidly breaking down and causing a slight ammonia rise. This is just theory based on what you have stated. Admittedly, I have no experience with food releasing ammonia so quickly. You’ll need to do your own testing to confirm the food is in face responsible for these ammonia spikes.

Thanks so much Ian.
We’re thinking of switching Betta’s sponge filter to a slightly bigger one — what would be the best way to go about doing this? Of course his current filter has been around awhile and has a fair bit of good stuff on it; we were just thinking it might be a bit too small.. being a Betta I don’t think we can run BOTH filters at the same time..

Can you run both on the lowest setting? Or reduce the input somewhat, say with a sponge or something similar to slow down the flow?

Possibly, though it’s going to start being kind of cramped in there haha… Do you mean to run both together for a period of time, or forever?

But it has to be connected to a working pump, yes? As in, the filter needs to be functioning in order to colonize? Not just sit there?

Hi Ian,
Could any of these cause a re-appearance of ammonia in a cycled tank?
1) Gunky filter
2) Dirty gravel
3) Underwater walls and floor that have pretty much never been wiped because they don’t *look* dirty.

1 and 2 could, but only if you weren’t performing regular maintenance on them.

3, not so much.

4. Certainly. Overfeeding is one of the most common causes of ammonia spikes.

Sigh. Well we cleaned the gravel and the filter anyway (gravel didn’t seem gunky at all; filter mildly). But I suspect it might be the overfeeding (enthusiastic kids)… Does this mean a “mini cycle” thing?? Please advise on how to treat, thanks so much.

The only way to really treat it is to administer the correct dose of Seachem Prime. The beneficial bacteria will do the rest. Because your tank is already cycled, you just want to limit the stress placed on the fish while your bacteria catches up to this “extra amount.” It should be done in a day or two. You can skip feeding for a day to help, many fish can last up to a week without feeding, this will ensure that no additional ammonia is added while your tank is catching up.

A water change won’t hurt. In fact, it’s only a good thing, especially if you have cleaned the tank to remove any additional food or poop. I usually give the advice of water conditioner first because it solves the problem immediately, as far as the fish are concerned. From here, you can monitor your tank and use the test kit to make the call on how to proceed.

OK, it’s weird question time. I’m just wondering how imperative it is to regularly clean Betta’s gravel. Can we just not? I mean, I know people generally clean their gravel because of poop and food debris, but I honestly wonder how much of that is in Betta’s gravel. He’s such a clean fellow — doesn’t drop any food (literally watch him eat his pellets) and then we just siphon up his occasional poop (almost as easy as picking up rabbit poop — it’s that “whole”). The times I’ve given his gravel a “proper clean”, I’ve just wondered why am I doing this; there’s no visible gunk and the water’s pretty much clear. And then of course in the back of my mind I’m thinking of the good bacteria families happily living in there……

I highly recommend it as it can cut down on future problems. Gravel vaccing, once you have a handle on it, should just become part of the water change, since you can siphon and clean at the same time. Consider it like vacuuming your carpet. Sure, you can skip a week or two or even a month. No real harm done. But anything that lands in your carpet is going to work it’s way deeper to the point where a vacuum isn’t going to be able to reach it. This stuff builds up over time. Again, you shouldn’t be worrying about the beneficial bacteria in your substrate, the bulk of it will live in your filter. At the end of the day, it’s your call. Maintenance sucks, I get it. I do it on 4 tanks each week. But it’s part of the job.

Thanks Ian!
Ok, will continue with our routine. We don’t mind doing it, was really just concerned about removing happy bacteria families. Sometimes wonder how many of them get “hurt” or sucked away as we plough in there.

Thank you so much for this page. I’m among those who was told by a big pet store that I only had to wait 48 hours to add fish, so I’m now trying to run a fish-in cycle with 6 fish (3 guppies, 3 guaramos) in a 20g tank that I started 9 days ago – it showed its first ammonia (0.5) today and I treated with Prime. However – I also have a smaller, 5g tank that was newly set up, doesn’t have fish yet, and hasn’t started its cycle yet – it’s only been running for 2 days. Would my fish have a better chance of survival if I moved 3 of them to the 5g tank (guppies, I guess, because they’re tiny)? I somehow want to help all of them survive.
The pet store sold me a bottle of TopFin “quick start” bacteria – that’s why he said it was safe to add in fish right away – does that actually work?

Hi Allyson,

Classic Petsmart. No, adding topfin “quickstart” doesn’t automatically cycle your tank. The purpose of bottled bacteria is to speed up the cycle. It doesn’t instantly cycle or make a tank safe for fish. Going further, there are different strains of bacteria. The strain found in API quickstart or DR Tim’s one and only (it’s the same stuff, different label) are the same as the bacteria that form in a cycle. There is much debate as to whether other brands actually help speed up a cycle at all, but I won’t go into that.

As for the fish, I assume you mean gourami? Depending on the species, you may find that these fish are either best kept on their own or in male-female pairs. They are a mixed basket and there is no guarantee they won’t bully other fish in your tank.

A 5 gallon is too small for 3 guppies. I feel they will have a better chance of survival in the 20g. 5 gallon tanks are not good for much other than shrimp/snail tanks or a lone betta.

Thanks so much for this. Yes, the 5 gallon tank was originally purchased for a single Betta, and just hasn’t been used for several years. I’ll keep them all in the 20g and watch chemical levels carefully. Thanks for the informative webpage.

And yes, gourami. So far, all of the fish have gotten along without any trouble. Once the tank has cycled, can we add a few more fish to it? If so, are there ones you would particularly recommend? The store said 1 fish inch per gallon of water, but now I’m wondering if that was accurate given the other questionable advice we got.

Unfortunately, the “1 inch per rule” isn’t a good one to follow. For instance, an 2 inches of a Koi would be best suited for a tank around 60 gallon. Even your 3 guppies would be too much for the 5 gallon. Fish tanks always hold less than you think. I would be hesitant to add any more fish to your 20 gallon. I would recommend finding a smaller “independent” fish store and going to them for advice, they will list all your options honestly, since they rely on your fish living for you to come back. The big chains seem to just want that one big sale.

It’s over an hour to anything but the big box pet supply stores, but I’ll approach everything with far more caution from now on and will do my own research.

My tap water PH is testing between 6-6.5, which I’m thinking may work in the fish’s favor during cycling. But I’ll stick with the fish I have, watch chemicals closely, and do plenty of water changes. Three days in and so far, everyone looks okay.

That sounds like a better idea. I know all this can take a lot to take in at the beginning, but trust me, it definitely gets easier.

Just be mindful that if the pH gets too low (closer to 6 or under) it can seriously slow down the cycling process. It will still happen, it just takes longer.

Hang in there, even a “fast cycle” can take some time. It’s all patience from here on out.

Hi Ian,

So to follow-up on your advice to me on the Cloudy Water page…

“If I was in your position, I would perform a 100% water change and stop adding anything to the tank besides water conditioner. From here, attempt to carry out the cycle. If it’s a bacterial bloom from cycling, the cloudiness should come and go.

You would be at step 4 in the fishless cycle. Just keep monitoring that ammonia and keep it at around 0.25. From here, you should see nitrites within 3 weeks and from there it’s just more waiting.”

You stated I would be ** at step 4 in the fishless cycle** ? But I Have Fish in my tank? 4 Glow tetras 4 Penquin 1 African Dwarf frog and 1 Nerite snail? So you mean fish-in? cycle? Or am I not understanding something?

Also, I had 2 other thoughts.
I have been planning on getting an aquarium for my son after this was all settled. Maybe I get it early, set it-up and put them there until her tank is fixed?


I mentioned I had a filter issue at one point and used another filter. I have a 30 gallon aquarium I have never used. I bought it used from a couple who had goldfish but needed baby space.
I have the filter – I did use it 2x when while doing a wc my filter stopped working for a bit (forgot to unplug it before the water got lower). It has been sitting unused in a bucket still with the same carbon/sponge/bio? They were unopened until end of Sept. when I got my tank and found out it had no filter in the kit. I put the filter together and put it to use to get our tank started, until I got the filter that was supposed to come in the kit.

I thought I potentially could start-up that aquarium (vs. buying all new in such a short time – hard to do when busy with school and activities all week)? The thing is it is 30 gallons vs.16 gallons. Could I fill it half-way? I don’t have any rock or anything to put in it. There is some sort of white plastic base I could leave in? Not sure what it was for? Then I guess I could hopefully quickly prep it and keep them there until I get their tank back in order? Maybe that is best?

Either way I now have a bottle of Seechem Prime. I also bought some Aquarium glue just in case? I have never used a used tank? She said she put Vaseline in the seams to keep it ok? That was easily 7 years ago when I first got it from her. And hopefully just a rinse with hot water will be ok with this option? Sorry. Lots of ?’s here I know. The 30 gallon tank is 2 floors down. Not so convenient, but maybe best option if you think worth it? Only thing is in the mean time, what do I do about fish in the 16 g tank as is. Just keep changing water weekly or so? And keep an eye on Ammonia etc.?

EXTRA note: This evening the tank looks Even More Cloudy. 🙁 Goodness wonder if they are having trouble seeing the food? The tests came back: Ammonia .25? Nitrites 0 and Nitrates 5 or I guess 0 given my Nitrate-y tap water?

Sorry, completely my mistake. My old brain often gets mixed up when replying to so many different comments. You are correct, I meant fish-in cycle. Step 4.

Regardless of which option you choose, you still need to cycle both fish tanks. Whether you do fish-in or fishless, it won’t make too much difference, thousands of people have seen success with either.

If your tank is 7 years old, depending on how it’s been stored, it’s possible it needs a re-seal. This would involve cutting away the existing silicone and reapplying new. It’s quite a project. Aquarium glue won’t cut it. I’d seek expert advice on whether this is the case, as there is nothing worse than dealing with a water leak with a fully stocked aquarium. I’ve had a couple in my time keeping fish and it’s a stressful disaster.

Also, I wouldn’t expect to see any movement yet. Cycling is slow. I’d do what I said in the previous comment and discontinue additives. Follow the cycle instructions and react according to the test kit. Unfortunately, cycles differ and there are no “exact” instructions. Your test kit will give you all the clues on how to proceed.

Hi Ian,

So, I am not liking the idea of redoing the old aquarium. But I was thinking, as I would need to cycle the water in the 30 gallon anyway, maybe I get started on that and if I notice a leak as I am filling it or what, it won’t matter as my fish will be in the 16g waiting for a cycled 30g? Curious what the time-frame on that might be and can I just fill it up half-way for this purpose? It is like 18 high I think? 30 long?

In the meantime, my 16g was last changed I think on Wed. or Thurs.? Forgot to mark it down. Normally I would do at least a 10% water change. Again on Wed. or Thurs.? I am also due for a carbon change on 2/20.

Can I stick with this? Do you think there is any chance my tank IS cycled? I have tested since Fri night and keep getting Ammonia at .25 or maybe I AM reading it wrong and it is 0? Nitrate at 0, Nitrate at 0 (adjusted for my 5 ppm tap water)? Maybe I am reading that a little off too? Maybe it is slightly more than 5ppm?

I am SO nervous about a 100% water change as you mentioned. Will that shock my fish? Wipe out Any good bacteria I might have? That is why I am wondering about any chance it is cycled or trying to go with setting up the old tank as a temporary plan B?

We have somehow struggled along this far, I don’t want to kill anything off if I can help it. 🙁 Same readings came back today as last night/morning etc. since Friday. And cloudiness is still high like yesterday, but not worse yet. It does still have this weird yellow/green color. It doesn’t show in the vials prior to testing, but it is visible in a 16 oz. cup if I place it in front of something white.

Hi Jenna,

Again, it’s best if you change as per your test kit. Let that determine how often you change. Saying “just change this often” will cause even more problems.

If you are not confident doing a 100% water change, perform two or three 50% ones over the next three days. If you do a 100% water change, you want the parameters (ph, temp, etc to match) otherwise it will stress out your fish. Since you are a beginner, and it doesn’t appear you are confident, I’d probably stick with the 50%. A 100% waterchange is best done in an emergency. However, I’d classify this as an emergency.

A water change won’t affect your bacteria. Unless you forget to condition the water.

Also, I’d say that the next effort of cycling STARTS once the water is changed. Again, why I said to start here is it’s possible one of the many additives that have been dosed in the tank is responsible for hampering it.

If your ammonia is 2.5 and nitrates are not raising, your tank isn’t cycled.

I’d advise joining a Online Aquarium Forum if you want a community to talk to and gather feedback off. You’ll receive plenty of support here.

Ok. Thanks Ian. I did another 50% water last night (following the one last wed/thur?). Still not a lot of cloudy movement. I added NO chemicals other than a water conditioner. Morning readings same as ever. Ammonia looks .25 or lighter. Nitrite 0. Nitrate 5ppm or 0 given tap water. Just out of curiosity, I tested the Ammonia in my tap water. It looks the same the tank. 0-.25? Does that tell anything? Also, I feel like am readings always seem to look more like 5ppm for Nitrate and then at night they look a bit darker but maybe that is just the lighting? I did check out a forum online too thank you!
I just trust your judgement more. 😉

Hi Jenna,

I’d do a second water change, as we discussed earlier, we want to get rid of that yellowy stain almost completely, so we can see if it comes back. This way we’ll know id something inside your tank is responsible.

When viewing your test results, it should always be done in natural daylight, the color of your indoor lighting can seriously throw the results out. If you take the tests outside, you can be more confident in your results.

So, do another water change, then re-test your aquarium for:

Water temperature

And record these. That’s all we can do for now. After you record those, and you are confident you are testing in natural day light, we can proceed.

And forums are great, there are plenty of people just as knowledgeable as me there – plenty of people take this hobby really seriously! It’s a good thing for beginners looking for advice 🙂

So with all the testing and always getting the same results, I decided to get and try the green killing machine (as was recommended on Fishlore?). I got it Thurs. and as of Friday night could see improvement. This morning, it looks So much better! Can finally see details in the back of tank and I have not done a wc since Monday. Too busy and sick and things seemed ok or the same at the time. Also one more note, I was testing water am and pm – that was why the light was a challenge. 😉 sunlight vs. night lights. 🙂

All the best Ian!

Hi Jenna,

I’m glad that was an easy fix. But keep in mind that while the Green Killing Machine will fix the problem (the green/yellow free floating algae) it doesn’t fix the cause. Ideally, you wouldn’t want the free-floating algae to appear in the first place. Now you are testing correctly, are your water parameters as expected?

Yes, got it. Watching the feeding. Keeping up with water changes. I did check out AQ Advisor and noticed it recommended 26% wc every week and that my tank was 104% stocked?. :l So I will keep a close eye. Did manage another wc today and cleaned some more. Still a bit cloudy, but So much improved. 🙂 It’s the first time I have seen it get better without a wc. 🙂 And I skipped the bio on the wc. Just used the API Stress Coat+ water cond.

Parameters are as before every time the same or close? Ph 7.4, Ammonia – 0 or just a bit more but not .25 (which is the same as my tap water?), Nitrite – 0, and Nitrate – 0 or possibly a bit more but not fully 5ppm (given 5ppm is my base with tap water). Test looks darker than 5ppm but not as dark as 10 ppm.

That’s awesome to hear! I’m so happy for you. Sounds like you have gotten a good handle on it.

On the testing, if your nitrates are continually getting darker, then it’s possible your tank is actually cycled. I’d observe this over a week or two, without a water change, to make sure. You should see the nitrates visibly climb on your test over this period

Hi, Yep

Completely agree with you. This guide is for those that are having a “oh no, it’s too late” moment. Fish can be hard to return or rehome once they are in your posession.

Hello Ian,

I am having a huge ammonia spike currently, with 24 fish in our 60 gallon tank. we kind of screwed up on our water changes, and gravel cleaning for a month and a half (long story, but we learned from it). Now, our ammonia is at around 4-8 ppm. We have been dosing with prime a cap and a half, every other day, and vacuumed really well, and did a 50% water change. This tank is over 2 years old, guessing we lost our cycle. What is really confusing me is that the ammonia shoots back up after a water change (maybe takes a day), Nitrites stay at 0, but nitrates are going up as well. They were at 5, now they are around 20ish.. I was planning on doing like a 75% water change after removing all the decorations, and searching for a dead fish, or babies… or i dunno. Any recommendations sir? I don’t want to have our fish stressed out, but they seem to be doing ok for now. No signs of ammonia poisoning, or any distress.

We also started feeding them every 2-3 days since we noticed the ammonia spike.


Hi Greg,

Depending on what the 24 fish are, it’s possible your tank is overstocked, while your cycle could maintain it, now it’s crashed it’s causing difficulty.

It sounds like you are doing all you can do, 50% water changes will cut ammonia in half and prime should take care of the rest. Ideally you want ammonia around 4 ppm, anecdotally, many people report stalled cycles from too high levels of ammonia. Unfortunately, it’s just a water change, prime, repeat until your tank cycle re-establishes itself. I’d do what you were considering too, remove all decorations and give tank a big clean down.

That’s what I did tonight. It went from 8 to about 4. I’ll do another 50% tomorrow or Thursday. The nitrates are not from a cycled tank, they are the same as from my tap.. my next question is.. Could I take some gravel from our planted tank and throw it in the crashed tank to seed it? It had Ick last week and we are still treating it (not been a good few weeks for us or our fish)..

My tank is approximately 78% stocked with my current filtration.. 11 white and black skirt tetras total, 3 bosmani, 2 small angel fish,1 bristlenose, 5 serpae tetra, and 2 Siamese algae eaters. Running 2 HOB tetra ex70 with various media in them..

That being said, I know there’s gonna be a dollar a gallon sale starting Sunday.. might go pick up a 20 gallon for some of the smaller fish so I can lighten the bio load in this tank.. thoughts on any/all of this?

Ich as well? Ugh, it’s been a rough patch. I hope it gets easier! It certainly sounds like you have a handle on things.

Your thoughts are right here, gravel from an established tank will help speed up the cycle. By how much? It entirely depends. I have seen some tanks barely speed up at all while others are considerably faster. I guess the answer here is that you have absolutely nothing to lose at all by adding it.

Oh no, another dollar per gallon sale? Well, now I have to make some space in my house. If you are confident your tank isn’t overstocked then there isn’t a whole lot to be gained by splitting them up, unless you want another tank for more fish, this one will need to be cycled too.

So I recently (as in 3 days ago) performed a 100% water change. I was given bad advice from my LFS and install a brass gate valve on my reef system. After about 5 months of declining corals and fish i finally figured out the issue, copper at 0.25. So i did my water change and removed all filter media and live sand but kept my live rock (simply because its too expensive to replace). I did install new water, live sand and a bottle of Fritz live bacteria and will be running CupriSord. Question i have is how much if any will my tank cycle? And is it possible that the copper add in my tank from the gate valve would kill bacteria? I did have to put my fish back in the system, because i did not have a suitable quarantine tank. I have only 6 fish in a 93 gallon cube, no coral yet.

Hi Clay,

It’s hard to say. Anecdotally, I know some aquarists who have treated their display tanks with cupramine by accident (contains copper) and their beneficial bacteria inside the rock appeared to remain constant, they didn’t experience any crash at all.

Based on this, I would expect your situation to be similar. This is easy enough to monitor by testing for ammonia.

You were spot on to add cuprisorb, it will trap any remaining copper in your aquarium.

Thank you for your reply, it is great appreciate. I have found you to be very informative. If I may ask you another question, I did take a water sample to the LFS and my copper is still reading between 0.25-5. I guess it’s hard for them to know the exact amount. What do you think my next move should be if any, and is there an accurate way to test for copper? Seems like my 100% water change was a waste of time and money! 🙁

Hi Clay,

A copper test kit is the best way to determine copper levels at home. I personally use Salifert, but I don’t see why other brands would be any less accurate. The problem with your water change is that trace amounts of copper can still remain behind in the tank, as a water change will only remove the copper in the water. This is getting out of the scope of this article, which focuses on cycling. I would suggest creating a post at either reef central or reef2reef. Both are amazing forums and their community will easily be able to assist.

Hi Ian!
So sorry this isn’t quite related, but would you know why a guppy might keep staying at the bottom of the tank? He looks physically fine, swimming fine, and yes, water parameters all ok (zero etc), but he’s been spending the last couple of weeks basically acting like his cory tankmates! He used to be all “typical crazy swimming guppy”, so not sure what to do…any ideas?

Sorry Catherine, it’s not much to go off, he could just be a bad breed (many fish are sadly very inbred), having health issues or everything could be perfectly normal and he is just chilling. If he’s eating and otherwise seems normal, I would just roll with it. If he stops eating, or shows physical signs of disease, you’ll need to either treat or euthanize, depending on what the disease is.

Thanks Ian! Yes, just rolling with it. We even wonder if he just wants to spend more time with the cories lol

He has now gone back to swimming up top and other usual guppy things. We were really thinking he was trying to join the cory clique haha

Thanks for the update, Catherine. I’m glad it had a happy ending! Guppies don’t make good cories anyway.

OK Ian — back to the topic 😀
We’re thinking of upgrading Gup’s tank to a bigger one, about double the present size. The current tank is already cycled as you know; what would be involved in transferring them over to the new one please? I’m thinking it won’t be an entirely new cycle, but there would be some fiddling and stabilizing required? We’d put in the old water of course, and then add additional treated water to it.. ? And we would need a bigger filter I’m sure — how can we make use of the current one and not “waste” all the nice families living in it? Thank you!!

Hi Catherine,

You are correct here, it’s pretty much a case of transferring as much stuff over as possible, gravel, your filter, water, anything else, get it in there.

Your tank will likely still undergo a partial cycle, to what extent, I can’t say, all you can do is re-test daily and react accordingly.

If you new filter has room, you can place the sponge directly on top of the biomedia (say ceramic rings) and it will soon spread. Leave it here for 2-4 weeks. Alternatively, you can run both filters at the same time. I prefer moving it to the larger filter as this filter is rated for your bigger tank, the sponge filter (if I am remembering correctly) might not be.

Thanks a million Ian!

Actually I think we’ve never talked about Gup’s filter before (Betta is the one with the sponge). They currently have this (a larger size of this):

But I’m thinking of changing this to something better. It is very efficient in keeping things clean, but we’re having to *completely* replace the sponges inside every few weeks (it’s neat though — it has a layer of tiny pebbles, then a carbon sponge layer and then another regular sponge layer). The tank is 10-gallons, gup and corys — would a basic sponge filter like Betta’s be ok? Or…? (I’m trying to keep it simple cos the kiddos are responsible for upkeep).

Interesting filter, I have only ever used a GEX (same brand) snail trap and it was surprisingly effective. Are those pebbles porous? If they are then this is where your beneficial bacteria is hiding.

A sponge filter is fine. Just make sure you buy one that is rated for 10 gallons. Larger sponge filters are always better, more surface area for bacteria.

If you want to use a sponge filter, I’d add both the sponge and the pebbles in a filter media bag, place the new sponge filter on or next to it and place a airstone under the media bag, to ensure current flows through and keeps the beneficial bacteria alive. Alternatively, run both filters at once. Either or. Second option is likely easier.

Thanks Ian!
Yes, I think running both filters at the same time is easier. You do mean just till it’s all stable right? Not forever?

So a sponge filter is effective enough for them huh? I can’t go by how it works for Betta, as he really seems so much cleaner than them lol

Those pebbles are sort of porous I guess? They seem like regular substrate type gravel. But really — the families are in that? And not the two other sponges? With the implication that it’s fine that we have to keep chucking out the sponges every couple of weeks? (we actually do keep a bit of the falling-apart sponge squished in with the new sponge a few days after a change — would love not to have to do that really!).

Oh yeah, I’d say within a month you’d be able to remove the old filter.

Sponge filters are great! Easy to clean and should be fine for a 10 gallon assuming you buy the right size. You’ll still need to gravel vac though, no escaping that. It’s a chore but worth it.

Sounds like a new sponge filter is just what the doctor asked for, you have experienced first hand how easy they are to maintain. A lot of people don’t like them because they are ugly and take up tank space. But from a practical and even affordability view, they are pretty great.

Actually the sponge filter looks quite fine in Betta’s tank really — just a couple of strategically placed plants in front of it and “blends right in” haha

In truth, I don’t quite understand the importance of “Mechanical, Biological and Chemical Filtration”. The Gex apparently does all these, while I sense that the sponge doesn’t?

For overall ease though, the sponge really is great!

Wow, wonderful! Thanks Ian!
Do marimo balls count as “planted tank”? Certainly they do leave tiny bits of green fluff……. Perhaps that’s why the sponge is fine in Betta’s tank, which has no real plants..

Nah, that’s hardly a planted tank. Your sponge filter should be fine here.

Haha ok thanks so much.
So in summary, it seems to me that this upgrading thing actually involves just putting everything about their old tank into the new one, and then topping it up with more water. Plus a bigger filter. That about sums it up?

Yeah, you are definitely on the same page. It’s a lot simpler than my long-winded replies make it sound, that’s for sure.

No, you’ve been SUCH a help! Thank you soo much!!

Our new tank is coming in in a few days — we’re super excited 😀

Hello, I unfortunately got set up by the pet store with the idea of doing the fish-in cycle. if it doesn’t work I will only try the once and go to the preferred method. My question is about the seachem prime method. I added 4 tetra glofish to a 60 gal tank yesterday. Tomorrow I will begin testing for ammonia. Please correct the following if I misunderstood: as soon as I am picking up ANY ammonia traces it is time to start using Prime. I should use prime every 48 hours, increasing the dose after about two weeks when Nitrites become present. EACH time I use Prime I should mix with new water and do a 50% refill- so 50% water change every 2 days with prime once I detect ammonia. — Please let me know if I am off on this, I just want to make sure I have my next steps in order. Beyond this , since I am using tetras and not goldfish, it was recommended to me to add stress zyme + to help boost healthy bacteria growth- do you recommend this? if so , should I do the double dose recommended for new aquariums? Would I do this with my water changes or just once a week without a water change?

Beyond this : ) – 4 longfin tetras in a 60 gal tank – is this an okay amount of fish to use? I worried that I should have 5 or 6 to get the cycle going faster but I also have a tall tank with less surface area so I went with 4.

last ( I promise) if you think 4 is enough or have me go up to 5 or 6- if any of them die during the cycle, should I replace or wait for the cycle to complete to get more fish? I figure if ammonia levels are high I should not replace- but it seems like glofish tetras are a bit ‘hit or miss’ just due to stress when joining a new tank-, two sadly died within the first 12 hours. If they all die I would not replace and do the no fish-cycle– but once started I am not sure if it is best to keep the amount of fish the same, or to hold through with out replace even if I end up with one or two of the 4 to complete the cycle ( is one or two enough to complete the cycle?)

Your information is invaluable, I wish I had researched up front before making the purchases : ( but I am loving the hobby.

Hi Nathan,

Don’t worry, unfortunately, being given bad advice by pet stores is basically a rite of passage in this hobby – we have all been there. I would recommend buying fish from a local independent fish store if possible, these guys are better positioned to give advice as many are actively involved in the hobby themselves. Big box chain pet stores just don’t train their staff well enough.

The 50% water change is if your ammonia or ammonia + nitrite reaches 4 ppm (prime can only be dosed up to 5 ppm) so until then you don’t need the water change. You do a water change based on the test results, there isn’t a set schedule here and will vary from tank to tank.

Adding the beneficial bacteria “may help” but it’s no guarantee. You see, this stuff is only good if the bacteria in the bottle are alive. It’s also argued that only a certain strain of bacteria actually helps, which is the strain found in both API quickstart or DR Tims one and only (it’s the same stuff) whether you add this or not is up to you. The cycling method above doesn’t need it however.

I wouldn’t worry about the amount of tetra in regards to cycling. feeding 4 will get the cycle going in no time. If there is one thing fish love to do, it’s eat and poop. It won’t be long before ammonia begins to appear.

As for replacing them, this is a moral decision on your part. If it was me, I wouldn’t introduce a new fish to a tank knowing that it could very well die. I don’t have a lot of experience with glofish, but my basic understanding is they they are very inbred and quite sensitive to stress. You should be able to complete the cycle even with a single fish. Although you will need to keep in mind that the amount of bacteria that grows matches the waste produced, so once the tank is cycled, you should only add one or two fish each week, to give the bacteria a chance to catch up to the new waste being produced.

I have my fingers crossed that all your Tetra pull through. But please prepare yourself for the possibility that they won’t. It’s not uncommon for your fish to die off during a fish-in cycle even if you do everything right. Wishing you all the best!

awesome! you are so helpful! ammonia came in at .5 today, I did one dose of Prime on my 60 gal tank. I will measure tomorrow, and in two days I will dose again based on the readings and will begin testing for Nitrites. I decided I am going to attempt once to replace the fish who passed, while I am at the store I will inquire about getting credits in case these also pass, at that point I would like to end the circle of death and will tred on with one fish to complete the cycle.

Thank you for your help and the speedy response! I am sure a lot of fish are alive because of you. I am also sure that a lot of people stuck with the hobby due to your swift and helpful support.

Didn’t take long for ammonia to appear at all, right? It sounds like you are on the path to a successful cycle now. Even so, if anything does seem unusual or if something goes wrong, please drop me a comment here and I’ll attempt to provide guidance to the best of my ability.

Thanks for the lovely feedback. I appreciate it.

Hi Ian! A quick question please — does having a better/more efficient filter control nitrate levels better? Thank you!!

Hi Catherine,

I don’t really understand this question but here are my thoughts based on what I think you are asking. Assuming the filter is the appropriate size for your tank, it shouldn’t really have an impact. Given that the flow rate should be appropriate, the beneficial bacteria colonies grow in size to accommodate the amount of waste being produced. Nitrate is always the end product. If your filter is appropriate, then nitrate should always build up at a similar rate.

Yes, I think that about answered it Ian! I realise that nitrate is the end product and so reasoned that filter “power” shouldn’t have much impact. The kids were just trying to figure out why their nitrates were up to about 20ish within just 4 days or so (the bigger tank still hasn’t arrived yet) (figure a bigger tank would help some) and asked if getting a bigger/another filter would help any.

Hello, so I have been at a couple weeks now with fish in cycle relying on my one remaining fish to get me through the cycle for my 60 gal tank. No Nitrites yet but ammonia is at a little over .5. I have been testing every other day and adding a dose of seachem prime every two days when I test. After rereading I would like to double check- it says seachem lasts 24- 48 hours- should I be adding seachem prime every day or every 48 hours? or should I be only adding more daily if the lvls increase?

I made the mistake of moving some decorations around to give more hiding places for my fish, he did not like this- he spent the night gasping for air at the top, but has since gone to hiding behind the toys- his activity lvl seems lower- the last week he has been super active and friendly, not hiding at all and staring at me while I watch tv, now he seems mad like I breached his trust. could moving the decorations really have that much of an impact or do you think it is more likely that I am not using enough seachem prime?

Last- there has been a couple inches of evaporation- I haven’t added more water as I don’t want to disturb the balance by topping off with tap water. Am I making the right call or should I be topping off the tank? Is there a point where the water flow from the filter could be a problem with the water lvl dropping? Thank you for your help!

Hi Nathan,

I prefer to dose daily rather than every 2 days, just in case it wears off sooner because you didn’t dose quite enough, or you are running late. If you have a routine of 48 hours, then do whatever works for you. I only suggest every day as it allows beginners to be a little more sloppy since they are not yet in a routine.

At 6 weeks I would expect to see nitrites by now. Are you reading your tests in natural daylight? Indoor lights can lead to incorrect results. Also, is there any biomedia in your filter? Biomedia gives the beenficial bacteria a place to call home.

Gasping for air the surface is more likely an oxygen issue, unless your fish is a gourami, betta or similar then it may be normal – read up on labyrinth fish.

As for evaporation, top it off as you see fit. It won’t affect your cycle. Just don’t forget to condition any water you add – otherwise the chlorine will kill any beneficial bacteria and you will start the cycle from the beginning.

thanks you! Don’t worry I am on week 3 not six, I am expecting to see them (nitrites) any day now, hopefully I am still on schedule. lucky Benjamin Fish is back on track now too.he seemed sick for a night, hid for a day and now is back to his normal social self. It is good to know that I can douse daily, so far so good, but once I get nitrites and my lvls increase w/ ammonia I will begin dousing daily. once lvls hit the tipping point in the guide I will do the half water change (seems like the next big step). This may be a silly question regarding topping off the water- I am using top fin water conditioner, it says 1 dose per 10 gal- so if it looks to me that I am topping off about 5 gal should I use a 1/2 dose ? or is it implying I should use one dose per gal of my tank ie 6 doses, even though I am only currently replacing 5 gal of water? Thanks again!

Hi Nathan,

This is actually an excellent question. You dose for the amount of water. So in this case, 5 gallons would be a half dose. I highly recommend making the switch to seachem prime. It’s much more concentrated and lasts significantly longer. It also neutralizes ammonia and nitrites, which is very handy in an emergency!

Hello, I am using seachem prime, I was going to use the top fin water conditioner for chlorine when I top off the water. Are you saying I can mix Prime in a bucket of tap water and wouldn’t need to use the water conditioner as well? If so, I will hold off on the water conditioner until the cycle is finished. let me know if you recommend prime over top fin water conditioner for water changes after the cycle is finished and I will just get rid of the top fin conditioner. I was under the impression to use the water conditioner when adding tap water, and use the prime daily or every other day based on the test results. Also, do you have any advice on how to properly mix in water conditioner or prime when doing a 25 % or 50 % water change? it sounds like I should premix, I just wondered what this looked like and if you have tips or tricks for conditioning water outside of the fish tank. Thank you again, you are the best!

Hi Nathan,

Seachem Prime is a “complete” water conditioner, in addition to treating ammonia and nitrite, it also dechlorinates. It’s the only dechlorinator I use and I highly recommend it. Topfin is an instore brand, while I am confident it’s a re-brand of another water conditioner, based on testing a range of Topfin products in my reviews such as gravel vacuums and fishfeeders, they have failed to impress, their focus seems to be on cutting manufacturing costs (while charging you a lot) vs. performance.

I guess what I am saying here is that Seachem Prime can be your sole water conditioner.

As far as mixing goes, you simply add it to the water that will be added to the tank. So say you are adding 5 gallons of water, you would add .5 ml to the bucket. A quick stir and you are done. It’s that simple. If you are using seachem Prime I highly recommend investing in a pipette for accurate dosing, as you don’t need much at all and it’s difficult to accurately dose using the cap

Thank you for the advice! Since I am still using seachem prime (I have moved up to daily) to nuetrilize the ammonia ( still nothing else at week 4 now) and since my ammonia is at .5 ( I have a 60 gal tank) and the guide says to use a full dose for anything under 1- would I be safe to fill a bucket with tap water, douse it with the full cap of prime and use the water from the bucket to both top the tank and dose for the ammonia? With how slow it is going I have been scared to throw tap water in and slow things down further or start me over. I think one tetra for a 60 gal tank is maybe not producing enough waste to make things happen quickly.

Hi Nathan,

As long as the water is immediately added and not left to sit, then this should be the same as adding a dose directly to the tank.

Oh, it’s going to be slow with one tetra. If it were me, I’d I was in this situation, I’d actually go and add more tetra. I know it’s not ideal for a fish-in cycle, but tetra are schooling fish and generally do best when kept in groups of 6 or more. This will also produce ammonia at a faster rate.

Alternatively, I would re-home this fish and perform a fishless cycle and return it once the cycle is complete.

This is a judgment call only you can make. It’s also worth mentioning that the beneficial bacteria grows to the amount of ammonia being produced. After all, without more food, the colony can’t get bigger. So while the tank is cycled for a single tetra, it may not be able to handle more. This is why, after cycling, it is recommended that you add fish slowly, separating out the additions by days or even weeks so the beneficial bacteria can adapt.

thanks Ian! I am slowly topping off adding a gal or 2 of water each day with my dosing- I stir for about 10 seconds and then release the water in. I started with one tetra (well one that lived) after adding many that died from shock, after 4 weeks – I now have 3 tetras in there ( 2 that are very happy and one that hides all day , probably not happy without a proper school who was added about 4 days ago) I got tired of so many tetras dying in my attempt to build a school ( I think part of the issue is I have 3 male tetras so now I need to add like 5 females at once to keep the boys from stressing the girls to death when they are added) so yesterday I added 6 Danios- none of them have died and they seem happy. I will probably stop now with the 3 tetras and 6 danios in my 60 gal tank until the cycle completes then I will get back on track with building my tetra school- I will likely drop 5 females together to balance out the ratio and maybe go back to using prime for a few days to negate any rise in ammonia from adding 5 tetras at once. Let me know if this sounds like an alright plan, thanks again for all of your help.

Zebra Danios are actually hardy little fish. In the old days, before fishless cycles were a thing, we used hardy fish like Zebra Danios to do a fish-in cycle. In fact, it was often the only reason these fish were bought, they could easily survive the chemicals in the tank. Nowadays we know better, but I thought it might be an interesting tidbit for you as to why they are surviving better than your other fish.

That sounds like a good plan. It’s entirely possible that your 5 additions won’t cause an ammonia spike, but even so, it’s still a good idea to perform daily testing in the week after and add prime accordingly. Just react to the test.

Fingers crossed the rest of your cycle moves smoothly. If any other questions around the cycle arise, drop me a line here and I’ll do my best to help. Good luck!

Hi Ian!

I am not at the beginning of week 6,

Ammonia has begun to drop to a about .35ppm

Nitrites have been present for 4-5 days and have spiked to 1ppm or possibly a little higher

Nitrates maybe appearing, color seems to be a bit gold but very well could be zero. it doesn’t seem as bright a yellow as yesterday.

I used 2 doses of Prime with the numbers above. Let me know if I am off track, but so far so good I think : )

I have noticed brown smudges appearing in random places on the glass, it’s not common but it is in a few places, is this something to worry about?

I also wanted to ask if I should apply the dousing rule to Nitrates. my test goes straight from 0 to 5 for Nitrates . Do I douse with prime just as I would for Nitrates and ammonia? Or is removing water the only cure for nitrates?

Also, do you have any advice for right after when the cycle is completed? I figured I would wait a couple days and perform a 25% water change and replace one of the filters (considering it has already been 6 weeks of using the same two filters). I thought I would wash the other filter off in the tank water and put it back as to not lose my bacteria. I was going to wait another 2 weeks, replace the second filter and do another 25% water change. – but then I thought – is the water change the only wat to get rid of the nitrates? maybe I should do a 50% change after completing the cycle, wait a week and then start replacing filters? What do you recommend? Also, with my suction hose thingimabob to clean the gravel, is this something okay to do once a month if I am doing 25 % water changes every two weeks or should I do this with each water change?

In other words, I am looking for advice as to the maintenance I should do right after the cycle is completed to get caught up on cleaning, and also a good steady routine to follow once I can turn to a regular schedule.

Thank you for all your help, all three tetras are alive and social as are all the Danios !

Hi Nathan,

All of this sounds like your cycle is progressing as normal. The “brown smudges” are likely brown algae (diatoms) – these often appear when a tank is cycling and go away on their own. They may get worse before they get better. The only time this will need investigating further is if they are still there a few weeks after your tank has cycled.

I’m a little confused as to why you would want to remove your filter? Your filter should consist of mechanical filtration ( a sponge) and biomedia (usually ceramic rings) the biomedia is where the beneficial bacteria live. If you are talking about those disposable filter cartridges then I highly recommend sourcing a new filter, as those are a huge scam – they encourage you to throw out your beneficial bacteria. One of my current tanks has the same sponge from 9 months ago while the biomedia is going on 3 years old, and they are only been rinsed occasionally when they look overly gunky, the sponge is probably rinsed every month.

You perform your water change as per how high your nitrate levels are. Ideally you will want to get them around 10 ppm or less, so this may take more than one 50% water change.

Once done, you should be able to see out a week between water changes. Just how big the water change needs to be depends at the rate nitrate builds back up. I highly recommend grabbing a gravel vacuum to clean your substrate if you have a rocky or sandy substrate.

Thanks for the update on your fish. I’m really happy to hear they are hanging in there! 🙂

Thanks Ian. If I am understanding right, once the cycle is complete I should do 50% water changes weekly to get the nitrate lvls down which may be high once the cycle is done requiring several 50% changes in a row. once done, test and do water changes as needed to keep the nitrate lvl down, performing a change as it rises to 10.

regarding the filters, I have an Aqueon quite flow LED pro and yes it uses the replacement filter cartridges. I bought a pack of replacements when I bought it. It sounds like I made another pet store driven mistake. I imagine now is a bad time to switch, that I should finish the cycle first, especially being so close to finished? What do you think? this filter is large sized, it uses two filter cartridges at once, so my plan was to replace just one when cycle is done- wait 2 weeks and then replace the other- unless you advise otherwise I guess I will do this to get through all the filter cartridges I have and then upgrade.

Let me know if I should switch to a different filter sooner or if you see no harm in sticking with these until the cartridges I bought run out. also, what type of filter do you recommend I get as a replacement and any advice on switching to the new filter? would I be in danger of losing the cycle after all this work?

Just when you think you have your finger on everything, you find out you got a scammy filter : (

Hi Nathan,

Mostly spot on. Your nitrate may rise to 20 or 30 by the end of the week. The exact rate depends on food, amount fed, other gunk etc. In a perfect world, we would keep it less than 10 in a non-planted tank. However, this is often not possible. Unfortunately, it all entirely depends on your tank. But if you can get it back well under 10 each week with a 20-40% water change, you are doing just fine!

On the filter, is there any room to add ceramic rings? If so, I would add these to the cavity before you replace the filter cartridges. Ceramic rings last for years before needing to be replaced, I highly recommend wrapping them in a filter media bag. It will make rinsing and replacing sooo much easier. Your future self will thank you. Does the filter floss on the cartridges look exceptionally dirty? If flow isn’t obstructed, my personal opinion would be to add ceramic rings and leave these disposable cartridges in for another month. This will give enough time for the beneficial bacteria to form on the ceramic rings. From then, I would remove one. Then I would remove the other and replace it with some coarse sponge followed by a block of filter floss (finer sponge) You will likely cut it to size, but these giant foam blocks can be purchased from amazon and are very affordable when compared to replacement filter cartridges.

Don’t worry, you are not alone in making this mistake. Really, these products should not be stocked at all. Fish keeping is the only hobby I have ever been involved in where store employees and manufacturers are sometimes not looking out for your best interests.

Hi Ian,

I am approaching week 8 and I think my cycle is completed or maybe destroyed but hopefully not?. I waited too long to check the last post, I ended up taking out one of the cartridges, waited 4 days and replaced the other cartridge. they had been in there for 7 weeks. I washed the old cartridges off in a bucket of the tank water, and washed the new ones in the same bucket of tank water before adding them. at this point my nitrites had spiked to above a little over 2ppm. ammonia was at .1 and nitrates seemed to be like 1ppm. this was 4 days ago, I was about to do a water change for the first time. But then they began to fall. the last 2 days the nitrites have been decreasing down to 1ppm 2 days ago, .5 ppm yesterday, and under .25 today. My concern is my nitrates still seem really low, like 2ppm- 3 tops. I was expecting to have really high nitrates and have to perform a water change soon. do you think I am approaching the end of my cycle? or did I mess up when I replaced the filter cartridges?

as a reminder incase it is useful, I have a 60 gal tall tank, cycled 2 weeks with one tetra, added a second tetra at 3 weeks, a third tetra at 4 weeks, and 5 danios in the 5th week.

Ian you rock!

Hi again Nathan,

Fingers crossed it’s close to being finished. I would hate for you to go back to the start after being so patient with the whole process.

Unfortunately, the only way to tell is, well, more waiting. If your nitrites drop to zero, ammonia stays at zero and your nitrates are increasing, then yeah, you are done. If the nitrates remain static (say over a week) then something could be amiss. But based on the information you have provided, it could possibly be on the way to being cycled. I would have been expecting higher nitrates too, but not everyone experiences the cycle in the exact same way. All you can really do is keep testing each day and see how each chemical (ammonia, nitrite and nitrate) moves.

Thanks Ian!

I believe my cycle is complete, Nitrates are still low like 1 or 2, but everything is else is at zero. I chalk it up to doing 4 weeks of the cycle with one tetra, having a 60 gal tank with small fish, and maybe using the stresszyme with bacteria which says slow down the need for tank maintenance. I am still testing every other day to keep an eye on things, but so far the only thing strange is the low nitrates. Thank you so much on helping me through this process!

Hooray! I’m so glad you made it. Based on what you are saying, I’d say the tank is cycled. It’s time to add fish. Just make sure you do it really slowly, as doubling the amount of fish or getting bioload heavy fish can cause ammonia to spike and the cycle then has to catch up. As always, your testing will let you know how to progress and react.

Congratulations again, it’s your patience that got you here!

Hi Ian,
Another quick question today please — at what nitrate reading should one do a routine water change? (sorry, I know that was really grammatically awkward). We’re trying to establish a water change routine for Betta’s tank and have been doing readings every day. It’s been amm and nit zero for some days now, and today nitrate 10 (possibly bordering 20? stupid colour chart haha). Oh and by the way, once amm and nit are zero, we can stop the daily prime dosing thing right?

In an ideal world you would want to keep it below 10. However generally speaking, the upper limit is around 40. In the right sized, correctly stocked tank, your weekly water change should be all that’s needed to stay on top of this.

As for Ammonia and nitrite reaching zero, you are spot on. That’s the end of your fish-in cycle.

I have a 55 gallon fish aquarium with three fish it took three months to get it where it needs to be using your method it’s finally got perfect water everything is perfect but I bought a 75-gallon I don’t want to start over and wait three months can I just transfer everything from a 55-gallon like the water the filter the plants and decorations over to the 75 gallon and be okay and then put my three fish back in their 75 gallon

Hi Mindy,

Congratulations on your patience! The short answer is Yes. However, be mindful that your current filter may not be powerful enough to turn over the water in your larger tank. The beneficial bacteria that grow in your filter are the deciding factor in biological filtration, and if water isn’t reaching them at a fast enough rate, then ammonia and nitrite can build up. You’ll want to monitor ammonia, nitrite and nitrates as before and react accordingly.

If the filter is too small, run a second, more appropriate sized filter at the same time. This way the beneficial bacteria can colonize that.

And most importantly, don’t add any more fish until you have the new tank under control. I know it’s going to be tempting, but it’s important you achieve balance first. Unfortunately, more patience will be needed here on your part. Much of fish keeping is just waiting. It’s why I like it – it’s a peaceful hobby.

Hi Ian,

I just bought a 60 gallon tank on Saturday the 30th of March. I set everything up that night and had yet to buy any fish. I rinsed my 75 pounds of heaven really well, placed it in the tank 5 pounds at a time (as this is how much I rinsed at a time) put the recommended amount of topfin conditioner for the 60 gallons and then added my water. I then placed all my decorations 2 bubblers and fake plants then on the 3rd day, after testing my water, bought 6 black skirt tetras and acclimated them to the water. The next day, 24 hours later, I tested, with the API master tester, again (this is something I do religiously). So far I have always had my readings come out at:

pH: 7.0
High range pH: 7.4
Ammonia: 0 ppm (initial test before fish was 0.25)
Nitrite: 0 ppm
Nitrate: 0ppm

Yesterday, April 2nd I bought some Seachem stability to promote bio-filter growth. I am following the directions explicitly.

My questions are

Should my levels constantly read what they are?

Is there anything else you would suggest I do?

Would it be beneficial to add a sponge to my marineland penguin 350 intake? I am already using 4 filters in the filter basin.

I’m sure I will come up with more questions does the road, but I am also asking small fish store owners their opinions as well. Plus I’ve found an employee at PetSmart who is an enthusiast and was the one who suggested the Seachem (along with a Redditor from the aquarium subreddit.

Thank you,

Hi Ryan,

If your nitrate is at zero, and remains at zero then your tank is uncycled. Zero nitrate is a bad thing, as it should constantly be increasing until a water change is used to lower it.

If your nitrate isn’t increasing, then your ammonia or nitrite should be. This is a clue that your tank is in the cycling stage. I would double check your testing, following instructions to the letter, and ensure you are reading your tests in natural day light as the glow from indoor lighting is poor for color rendering.

I always prefer to add biomedia to the main filter, you can never have too much biofiltration and if you want to start a new tank, or know someone else who does, you can donate this to speed up the cycle of the new tank – as long as your tank is fully cycled.

To me, your priority is figuring out what is going on with your testing, as at least one of these shouldn’t be zero.

Hi Ian,

Thanks for the quick reply.

As far as the testing goes, I am following the instructions to the letter (carrying the instructions with me as I perform each step). I set up times with Alexa for each phase, from shaking the bottles of solution to time to mix once in the test tube. The only thing I don’t do is check it in natural daylight. I’ll give this a try today to see if there is any difference. At this point I’m just thinking that the tank is still developing it’s cycle and hasn’t kicked off yet. I will continue to religiously monitor it though.

I did notice my tank got a bit cloudy last night. Im hoping that this is a bio bloom brought on by the Seachem stability but actually believe that it is because I was experimenting with some pellet food in an automatic feeder, it sent out a lot more than I expected it to. That won’t happen again. I’ve also lowered the feeding cycle to once a day and may cut back to every other day. Do you see any problem in doing this?

Thank you,

In a fish-in cycle, it should only take a few days at most for measurable ammonia to appear, if you are feeding as usual – fish are ammonia producing machines, this is why my default thought was to question the testing process.

“Bacterial Bloom” or “Clouding” is common in the early stages of the cycle, it usually goes away on it’s own once these tiny bacteria run out of food. If it’s this, then it’s a harmless and somewhat expected.

Oh, and a tip on the automatic fish feeder, Use tape to cover half, or a third or more of the opening – The default small setting on most automatic fish feeders is often still too large for small pellets. Keep experimenting until you find the right amount of tape required, it’s a trial and error thing. Also, if it’s a rotating feeder, the amount it dispenses will vary according to whether it’s full, half full or nearly empty – another thing to keep in mind.

Cutting back feeding is fine. Most fish can last up to a week without food. In the wild, a hand fed meal wouldn’t come along every day. Doing so will slow the rate at which ammonia accumulates – the more a fish eats, the more ammonia they produce. This is somewhat desired in a fish-in cycle since rapid ammonia buildup can be harmful.

Great! Thanks for the advice. I did another test around 8 this morning, the test results (using the daylight) offered no different results, except the ammonia, which looked to be between 0 to 0.25 on the color chart. Still zero nitrites and nitrates. The fish seem relatively happy. A couple of them are very busy swimming back and forth. The others are more docile, but still very active.

As far as the auto feeder goes, I found that out yesterday, except it was the first slot that didn’t put out enough food and the second would feed an army. I like your tape advice. I think I’ll give that a test run. Right now it seems to do will with the flame food I’ve got.

Also on the feeding I think I’ll leave them at 2 meals (possibly 3) a day.

Thanks again,

Sounds like you have it all under control now. Unfortunately, from here it’s pretty much a waiting game – while it might test your patience, it will be worth it!

Ammonia is what I would have expected to see by now and it’s basically the starting point. Everything sounds positive here!

Here is an image of ammonia progression note, that this will look slightly off depending on your computer screen, but it should give a rough idea as to how colors progress as ppm increases!

Hi, If I have a 29-gallon aquarium, what should the daily dose of prime be? The container says 2 drops per gallon. Thanks in advance.

Hi Jean,

The instructions on seachem prime should say “1 capful (5 ml) for each 200 L (50 gallons)”. If your bottle doesn’t say this then it isn’t seachem prime. so 3 ml would treat 1ppm in a 29 gallon.

Hi Jean,

I’m a little confused about your bottle, I just bought a new one last week and it still says 1ml = 10 gallons. The Seachem Prime website still has these exact instructions too.

2 drops per gallon would be considerably more than 1ml/10gallons.

I’m not saying this to be petty, it’s important to figure out what is happening here as if it’s seachem prime and it’s concentrated then you are at risk of dosing too much and harming your tank. If it’s not seachem prime, then it might not work at all.

It says “Prime Seachem Removes Chlorine and Chloramine” “Detoxifies ammonia, nitrite & nitrate”

Looking at it well it does not say exactly the same but, its the same brand … Should I buy the one you indicate to go safe?

Hi Jean,

Thanks for clarifying, I have never seen this before. That is Seachem Prime, a member of my club pointed out that it has a dropper head? Is that correct? If so, then my sincere apologies, as the instructions are correct.

If it says 2 drops per gallon, then you will need to count out 58 drops each time you want to treat the whole tank. It is for this reason I would recommend using a larger bottle and buying a pipette, counting out that many drops is going to get tiresome really quick.

I have never bought the small bottle and was unaware that this was the case. My apologies for the mix up.

Dont worry, and yes, that one.

58 drops daily during cycling? .

Then I will buy a bigger bottle without any doubt.

I know, I had to double check (29 x 2 = 58) I think the small bottles are designed for tanks under 5 gallons. It seems like too much effort for anything larger.

Definitely, thank you very much anyway for helping me clarify. Sorry if my English is not perfect, my first language is Spanish, but good information is not obtained in that language.

Jean, don’t worry, your english is amazing. I never would have guessed it wasn’t your first language 🙂 I’m glad we could get to the bottom of it!

Hi, I’ve been 12 days, I still do not see nitrites, is it normal? If it is not normal, what do you recommend?

By the way, I’m using “Microbe-lift special blend water care” in addition to “Seachem Prime”

Hi Jean,

It depends. Do you have a filter with biomedia? The beneficial bacteria ideally needs somewhere to grow. The beneficial bacteria supplement may or may not impact the speed of your cycle at all, but it certainly won’t slow down the appearance of nitrites.

It comes with my aquarium

The manual says this.

Complete 3 Stage Filtration System: In Stage 1: • The filter cartridge floss screens out dirt and debris. • Molded and ribbed back for maximum water-to-carbon contact. In Stage 2: • Activated carbon inside filter cartridge removes odors, discolorations and impurities. • Change the used Aqua-Tech replacement cartridge monthly as carbon deactivates with use. In Stage 3: • The Bio-Tech Biological Grid*, which comes with your power filter, never needs replacing; ensures elimination of toxic ammonia and nitrite; and has a unique design that will not clog!”

I’d suggest adding some ceramic rings, I personally use Sera Siporax and I know they make a “mini”version for small filters. If you need more room you can replace the “activated carbon” stage 2 and eventually stage 3 (after cycling)

Also, what are your ammonia levels reading at?

Ammonia is 3ppm

Then I eliminate the filter that has activated carbon inside, then I put the ceramic rings? And later eliminate the third part? How do I replace that part? With what?

The third part “claims” to do the same as ceramic rings, except it’s plastic and does not hold the same surface area. If your ammonia has not decreased yet, then you could probably replace stage 3 with more ceramic rings right now. However, once the ceramic rings are in, I would say that is “day 1” of your cycle.

With 3 ppm you should soon notice a decrease. I assume your pH and temperature levels are okay?

Hi Jean,

Carbon only removes bad smells, medication and tannins. It doesn’t hold waste. The filter floss which is rinsed holds the watse.

Okay, okay now I understand, and yes Ph and temperature are set.

I’will buy this ceramic rings


Hi Ian! I have some free time today so I thought I’d bring you up to speed on the “cycling tank with healing fish” affair. You may be fascinated to know that since my last report, Betta’s tank is all cycled and he is continuing to complete recovery ^_^

His fins are about 93% regenerated; just has about half a centimeter to go. Honestly, considering all he’s been through, I’m just grateful he is doing fine now and we’re just so happy for him to be living comfortably in a cycled tank. I wish I could share with you pictures of when we first adopted him – I am not kidding when I say that ALL his fins were GONE. They had literally fallen off almost right at where they connect to his body. There was even one afternoon where I actually SAW a chunk of his caudal fin fall off. I’ll never forget how there were a couple of days where he was really on the brink, barely breathing or moving. So praise the Lord that he is all fine now!

Which leads to how we cycled the tank. Hopefully this may prove helpful to someone else out there in a similar situation 🙂 Ok, so really, I believe the first step is to get the fish proper treatment. And by that I mean proper antibiotics prescribed by a vet, ideally a marine vet like ours is (yes, he actually treats dolphins and so forth as well). Because really, if after 2 or 3 days of salt or whatever other pet store remedy you apply doesn’t work, you can pretty much accept the fact that it’s just not working, and will quickly go downhill if you don’t do something fast. So yes – proper meds.

Then, the pristine water conditions. If you recall, we were doing water changes, TWICE daily, one in the morning, and one in the evening, PLUS dosing with Prime. Naturally ammonia and so forth remained at zero because the water was being changed so much. But if you recall, the moment we tried doing it just once a day, the fins would show new signs of ragginess the next day. The conclusion was that for so long as he was still healing, he needed the water to be that clean. So we kept doing the double water changes, for weeks, months even. In the meantime, we also introduced sponge filters into his tank (he didn’t have any when he was on antibiotics). The obvious reason is so that the helpful bacteria have somewhere to live. So he got not one, but two sponge filters (the air is baffled so that they’re very gentle).

Then, as we saw him getting more and more stable and regenerating much more, we decided to gradually lessen the water changes. By that I mean we gradually reduced the amount of water we removed daily each time by small increments, testing for ammonia every day. Of course, it eventually reached a point where the amount removed became rather negligible, so we decided it was time to reduce from two water changes to one. Which was essentially where it became like how we cycled Gup’s tank – one small water change every day until ammonia consistently read zero. And that is where we are now at last! His tank is cycled and we only do water changes about once a week.

And that’s it! Thank you Ian for being such a wonderful help, unfailingly! I recall wishing you a merry Christmas and new year, and now it’s already April lol.. it *does* take awhile. But don’t give up on your little friend, people; it’s all worth it! ^-^

Wow Catherine,

What an adventure, you are right, it’s April and time has flown… Although I’m sure it didn’t feel like it to you while you were being so diligent day in day out. Congratulations on you successfully (well, almost!) recovering your betta from fin rot. I don’t say this lightly: You are amazing!

Thanks so much for sharing your process in so much detail, if anyone else asks about finrot, I’m going to direct them to this comment. I wish you all the best for the future and if you need any more advice, you know where to find me 🙂

Thank you so much Ian! “Adventure” is right loll.. I think it would be more apt to say he’s 95 to 96% regenerated, as it’s just that little bit left to go. I forgot to add that we did briefly try that Boyd Vitachem thing, but honestly, I don’t think it did much at all. Good water quality is really the thing I think. We’ve also concluded fins grow back at about 1mm per week haha..

O! and re upgrading Gup and co to their bigger tank – it was easy. Yes, literally like how you said – just put everyone and everything into the new tank and add more water and appropriate filters. We’re running the new sponge filters alongside the old ones still – I think about a month in all should be ok?

O, and could I please just check with you again – unless the sponge filter looks gunky, is washing it every 3 weeks or once a month ok? Or should it be more frequent, like fortnightly? There’s literally nothing visible on them..

Wow, no wonder it was such a long process, coming from stumps at a rate of 1mm a week is sloooowww. Again, you are awesome for having the patience to see through this recovery period.

I’m glad to hear the bigger take migration didn’t cause any issues. I didn’t think it would, but you never know – sometimes these things just go wrong for no reason at all.

As for the sponge filter frequency, it entirely depends on your rate of build up. As long as rotting gunk isn’t being trapped, and flow isn’t obstructed, then there isn’t really a need to clean it more frequently. When you place it in a bucket of tank water and squeeze, it should turn the water brown – that’s how you know it’s ready for cleaning.

Thanks so much Ian! Yes, we squeeze the sponges every couple of weeks and the water is perfectly clear; we just feel like we’re squeezing the nice families on them for nothing lolll

Re the new sponge filters running alongside the old ones in Gup’s tank — is 3 weeks or a month together enough to transfer sufficient good bacteria do you think? We’re not mad about having so many filters in there haha

I get it. Besides, no one likes to do more cleaning than they need to!

Haha, Gup must be so confused about all the filtration. If it’s been 3 weeks, I’d remove one, wait a week testing daily to confirm everything is normal then remove the next and repeat, until you are at just the one filter.

Yay, thank you so much Ian!! I’ll take note of the timings and all and let you know ^_^

I just realised that saying “Naturally ammonia and so forth remained at zero because the water was being changed so much” was not right. I recall now that the tank *was* cycling during that time, even with the daily double water changes. There *was* ammonia and then nitrite etc etc Remember my asking you if it was truly cycled when the ammonia and nitrite were finally zero, and you essentially said it was as cycled as it could be in light of the double changes? So yes, one does have to endure that cycling process. Subsequently reducing the water changes in small increments (literally about 50ml each time) made the remaining cycling easier and more bearable 🙂

Thanks for such a wonderful article. This is very helpful.

I have Prime and am a bit confused about Step 2 as I used Prime to remove the chlorine when I initially added water to my 10G. Should I replace all the water and use a different product for Step 1 since Prime reduces ammonia?

I think I follow the rest of your steps. Thanks again!

Hi Jeff,

Prime can be treated as two seperate products, one as a dechlorinator, the other as a treatment for ammonia and nitrite.

Simply add as much is needed for the water change and if that is also enough to treat ammonia and nitrite, then you are done. If it’s not enough, add the difference directly to your tank. As long as you are adding your dechlorinated tap water immediately to the tank, you can add it to the total.

Does this make sense? Let me know if you need any more clarification.

Hi Ian

This is a wonderful article. I saw this only when I ended up in the unfortunate fish-in cycling.
I am from South India, Mine is a concrete pond with 7000L capacity, but I believe the cycling theory applies same to pond as well. I have filtration and air pump installed in the pond. I have now 5 baby Koi fishes and some molly fishes in my pond. My pond is 2 months old, Kois were added only a month back, before that I had only Mollies for testing . Till before 3 weeks I had the problem of single cell green algae which I believe has eaten all the ammonia produced and blocked my pond from cycling. Around a month back I started using UV in my filter, so the algae got cleared after a week of that I lost a baby koi, just morning it started behaving ill, and I lost it in the evening. Then I tested for Ammonia and it was around 0.5ppm and I believe the Ammonia killed it. Then after searching on the web I learned more about cycling and this article is the best among all.

Now I am watching my water parameters regularly for the last 2 weeks, recently for the last one week, I have Ammonia 0.25ppm, Nitrite 0.25ppm, Nitrate 0.5ppm and my pH is stable at 8.0 and KH is 5 drops(89ppm). I am using Seachem Prime/Safe to detoxify Ammonia/Nitrite/Nitrate. Since it is a pond its a bit costly affair to use the water conditioners, but water change even the 10% means 700L in my case. But I guess I have no other choice. I am using the API test kit for measurements and I also have Seachem Ammonia alert bought 2 days back, it always shows the safe range till now. I have reduced feeding once a day for the fishes, reduced the quantity a well.

With these details, can you please tell me whether I’m in the right direction, I just need to continue monitoring water parameters waiting for the pond to get cycled.

Hi Renjith,

You will have to forgive me here but I have no experience cycling a pond. However, I would be surprised if the ammonia was eating by free-floating green algae. Based on my knowledge of tanks and not ponds I would say it’s far more likely that something has happened to kill the good bacteria in the tank, which would cause the cycle to reset.

The Seachem Ammonia Alert is one of my least favorite ways to measure ammonia. It can vary with it’s accuracy, from my experience so be careful when relying on it. Their liquid test kit is much better.

Everything you are doing is sound for a tank. If it’s progressing, for the next step you should notice your ammonia start to lower, your nitrites and nitrates rise.

Tjanks Ian. I understand.
If its not algae, I am not sure what reset my cycle, I was not aware of the cycling thing when I started so I did not measure the water parameters except PH then.

But let me confirm one thing. Though in less quantity, is it usual to have all Ammonia/Nitrite and Nitrate all together in a tank/pond for a week. My fishes behave normal and they eats food as well.

And regarding Ammonia, I rely on API test kit primarily, Seachem Alert is only used as secondary.

You are correct, it’s common for all of these to appear at once, but their levels shouldn’t remain constant. In a tank setting, ammonia and nitrite should eventually decrease to zero (not at the same time) and nitrate should rise. However, I would still recommend reading up on what happens to nitrate for ponds- since ponds don’t use water changes, something else must happen!

I’m glad to hear you are using the API test kit, it’s my favorite! Good choice!

Hi Renjith,

Thanks so much for sharing. I looked at your videos, those are some beautiful Koi!

Hi Ian-

I thought I’d give an update on my fish-in cycling and Betta. I posted on your other cycling blog and your responses were very helpful. I decided to try Tetra Safe Start in hopes to get a jump start on the bacteria. It’s been a couple weeks and I’m getting readings of 5-10 ppm Nitrates. Ammonia never went over .50 ppm (I’d dose with Prime accordingly) and I never showed Nitrites in any of my tests. Ammonia has been zero for at least 6 days. The water is clear but the top had a slight cloudy surface and was a little slimy like algae, but clear. I brought a sample to a local fish shop they they thought it might be from the Tetra Safe Start and weren’t concerned but recommended a small water change which I did. It cleared up but seems to be slowly coming back. Is this normal and an indication that bacteria is present? I also tested the PH and it has gone up from 7.2 to 7.6. Is there a product you recommend to lower PH and at what level does it need to be done. So, based on this information, is it possible the tank is cycled?

Also, how often do you recommend cleaning the tank with partial water changes, vacuuming the gravel, scrubbing the sides, cleaning the silk plants etc.?

On another note, I noticed a lot of little bubbles on the water surface. Did some online searching and found that my Betta was making nesting bubbles which I read was a good sign of a happy healthy Betta.

Hi JJ,

That film on the surface could be due to a lack of water movement. It’s likely oils from food, poop slowly building up. When you performed a water change, it’s possible some of these oils were removed, causing it to clear up. This is common in betta tanks and can easily be resolved by adjusting the flow of your filter or placing a small airstone (with low air flow) where the buildup occurs.

If your ammonia and nitrites read zero, and your nitrates are continually on the up and up, then you are correct, your cycle is done.

Cleaning the tank is done according to your tests. Generally speaking, you should be doing a water change once a week (gravel vacuum at the same time, since it’s done in a single motion) plants and sides are once they gunk up and look visibly dirty, or when you feel like it.

Congratulations on finding a bubble nest, it is indeed a sign your betta is happy and healthy. A sign that you did a great job cycling your tank 🙂

Poor water flow makes sense for causing the film on the surface. I have a Fluval Spec V 5 gallon tank and the pump it came with has a really strong flow even on the lowest setting. My Betta was being pushed around and avoided that area in the tank. So after researching online for solutions, many people with Bettas posted that they use a Fluval pre-filter sponge which greatly reduces the strength of the flow into the tank. Unfortunately, it may reduce the flow too much leading to the film but not sure what else I can do as I’d prefer not to buy a different pump. I don’t mind doing water changes to remove the film but if having a low flow could lead to other issues, please let me know!

Thanks again for your help & advice!!

Oh, if the filter is a single unit that came with your tank, adjusting the flow will be significantly more difficult. With a normal HOB or external filter, you can modify the return to reduce the flow while keeping the surface water agitated enough to break up these oils.

However, if you are on top of your weekly water changes, it shouldn’t be too much of an issue. But if it builds up, it can reduce the amount of oxygen in your water (oxygen enters water through the surface water of the tank) in addition to your betta finding it more difficult to take his occasional gulp of air from the surface. If you find it building up too quickly, try swapping over to a different food, different foods have different “oil” contents. But in all honesty, if you are performing a weekly water change and not overfeeding I would be surprised if this reaches problem levels. Even so, keep an eye on it just in case.

In a 5 gallon tank, I don’t see any issues such as “dead spots” or oxygenation issues occurring for a single betta from low flow.

Hi Ian,

Another victim of pet store misinformation ????‍♀️

I’m on day two of fish-in cycling using the “Prime” method on my 4 gallon Betta tank.

I’m reading 0.5 ammonia, 0 nitrites and 10 nitrates. Why does it seem that my tank skipped a step??

Do I simply continue dosing and testing until 0 ammonia, 0 nitrites and 10 nitrates? And once I get there, when can I do a water change? Is 25% too much for a small tank?

Hi Barry,

Sorry to hear you found yourself in this situation. But it sounds like you are all over it.

While this isn’t common, it’s still normal – it’s possible your nitrite eating bacteria got established faster for whatever reason. Just keep progressing as normal, dosing ammonia until that too reaches zero. Your nitrates should increase the whole time.

You can do a water change whenever you want. As per instructions, whenever combined ammonia and nitrite reach 4ppm or to get your nitrates down to measurable levels. A 25 – 50% water change isn’t too much for a tiny tank. Generally you want to remove enough each week that it drops the nitrates below 10 ppm (closer to zero is better)

Whoops, I should have clarified that is using the seachem prime method.

Hang in there Barry, you’ll be there in no time. Good luck!

Try testing your water straight out of the tap.
You will find that there already 10ppm or even more in the water before you do anything to it.
It is far from unusual…in fact 10ppm Nitrates is the norm…

Hi! I am on day 22 of betta-in cycling a 6.7 gallon tank. My ammonia was VERY high the first time I tested it (it was a week or so before I started proper testing and education on proper cycing) — and I followed with daily 50% water changes until ammonia was down to a reasonable level. Then I learned about Prime and I’m on course now with the ammonia staying pretty constant at .50 (it’s been this level for 4-5 days). I continue to dose with prime daily. I have tested for nitrites about 7 or 8 times — and twice came up positive, which was very exciting. But then the next day, they’d be back to 0 which was odd. I even retested a few times, thinking my testing was off — but no. I’ve checked for nitrates 3 times — each time nothing. Should I just stay the course and keep waiting to nitrites to appear and rise? Or is there perhaps something else I should be doing to promote the nitrites? I would have thought I’d see more progress by now. But what do I know! lol. Thanks in advance.

Hi Kelli,

While the steps in the above article are how *most* people see their cycle progress, a few do experience it a little different. The start and end are the same, but the middle gets a little odd.

Ammonia levels that are too high may stall the cycle. You should start counting your cycle days from the day that your ammonia levels were in check. That’s day 1. From here, It’s likely more waiting. If you havn’t seen any movement in three weeks, then something may be amiss. It might be just a few more days waiting.

Also, not everyone experiences measurable nitrites. Sometimes it skips straight to nitrates. I’d double check your nitrate testing, following the instructions closely, as tap water often has some degree of nitrates in it anyway.

But by and large, it sounds like you are doing everything right. It’s just a matter of more patience. I know this part sucks, but you’ll get there!

I appreciate you taking the time to reply — thank you so much! More testing, more patience — Onward!

Hi Ian, so sorry to be posting here, but the system wouldn’t let me reply under my silicone post. This was what I wrote:

Thanks so much Ian! It’s a relief to know! (I can’t imagine using a razor anywhere near the tank lol; do people really do that?)

By the way, do you think new fish should be quarantined before being added to an established tank? We’ve honestly never quarantined anyone before — just floated them for a bit, then added them in. It seems to me a quarantine tank for a new fish might sometimes cause more stress than good? Yet it seems quarantining is advised? What are your thoughts? And if we must, how best is it done? Thank you!!

You would be surprised what people do – especially with those sharp algae scrapers.

I quarantine all fish, I believe this is important, especially in a community tank. You have no idea where your fish came from, the conditions it was kept or the hitchhikers or disease it may bring in. It’s easier to treat a single fish rather than an entire tank. Many people use different products. I use ich-x in my quarantine tank.

Thanks so much Ian. How long do you personally quarantine for? Do you mean you put in the Ich-X as a just-in-case? At regular dosage amounts? I’m a little concerned how to care for the fish for that short period in an uncycled tank…

Sorry Catherine,

I’m happy to have helped you this far, but this is too unrelated to any article on my site as of yet. If I start answering unrelated questions for you then It’s only fair that I do it for everyone. Unfortunately, I don’t have the time for that. I already spend an hour each day answering the related questions. There are plenty of good quarantine articles on the topic. “Michaels fish room” also has a youtube video on it. But i’m happy to help you with any other questions you may have that correlate to my published articles.

Hi Ian,

I’m so glad I found your article! I’m not sure if I’m doing this properly but my fish seem to be happier now. My fish have been in the tank for almost four weeks. One started having scale damage and acting really lathargic. So I started doing water changes more frequently to lower my ammonia. The highest it’s ever recorded was 1ppm. I’m now doing 33% changes everyday, adding prime and aquarium salt each time. I started heating the tank cause it looked like there was ich. I add stability once a week and also added a handful of rocks from a friend’s established tank. I got a piece of driftwood to lower my pH from 8.4.

I’m confused about my ammonia, nitrites and nitrates. My ammonia readings are about 0.5 ppm before AND right after the 33% water change. My nitrites have always read 0. But my nitrates are now reading 5ppm (although I question if the colored water from drift wood is affecting my readings).

So my questions are: do I keep doing the daily water changes? Why is my ammonia the same after a water change? Do you think I actually have nitrates in my tank?

Would you recommend moss balls once my cycle is established?

I’m trying so hard to keep my fish happy.

Hi Christina,

A fish-in cycle is never easy and it sounds like you are doing an amazing job!

Don’t worry, that colored water (it’s called tannins) from your driftwood won’t affect your test kits.

Are you using the API test kit to measure ammonia? I will use that as your example. So your ammonia currently reads “0.5” before and after?

A 33% water change will reduce your ammonia by “roughly” 33%. So in this case, your actual reading would be 0.335 (0.5 -33%) Now, since this is still above the next reading on your color chart (0.25) it’s can look like it’s the same reading on your color chart as before the water change. If you test in daylight rather than indoor lights, you will be able to match the color better (orange lights can make the colors look off)

Next question: Should you keep doing daily water changes? Absolutely. Ammonia is very likely the cause of your fishes scale damage. Scales will repair, but the better quality the water, the faster it will happen.

As to whether or not you have nitrates in your tank, it’s possible 5ppm is from your tap water. If you test your tap water before adding it to your tank, and it reads 5ppm, then this is likely the source of the nitrates rather than them appearing through cycling.

And I am sure you are doing this, but you are conditioning your water before adding it to the tank? Also, you have a filter with biomedia/sponge? This is where most of the beneficial bacteria will live.

I hope this helps!

Thank you so much Ian!

Makes sense with the ammonia readings when you break it down like that. I do all my water testing at night after the kids are in bed. Will keep samples for daytime testing.

Tested my tap water for nitrates – you were right there too!

I condition my tap water with seachem prime.

There’s a biowheel. Would you recommend using something else for biomedical? Would clay pellets work? I would love to eventually do an aquaponic herb. (Assuming my cycle eventually sets up!)

Thanks again!

Not a problem. My preference is for ceramic noodles, since these last for years and are easy to replace, but a biowheel filter is more than up to the task of cycling.

It sounds like you are doing everything as well as it can be done, it’s just one of those pain in the butt things that takes time until it’s finally done.

Thanks for all your help Ian! Really appreciate your time and how quickly you reply.

I have my fingers crossed it’s smooth sailing from here. Please drop me a line if you hit any stumbling blocks and I’ll assist to the best of my ability. Good luck!

Is it normal to have 0.50 ppm ammonia, o ppm nitrites, and 5.0 ppm nitrates? . Im conused. I had verry high of the 3 then cleaned out till i was at 0 for all 3. Im not sure what i was doing And have slowly built this up. Im not sure if my tank is cycling or if it has cycled already.? I have 13 fish in and im terrified to lose them.

Hi G,

If you test your water before adding it to the tank, is it 5 ppm? If your tank is showing measurable levels of ammonia then it probably hasn’t cycled.

Hi Ian,
Thanks for replying!! Okay so, I tested regular tap water and yes it does measure 5 ppm. So today is day 2 in this effort to cycle with fish and my levels of ammonia are not rising too fast but is at 0.50. Ive slowed down feedings. So at this point i have .50 ammonia and 0 nitrite. That given am I heading in the right direction? From this point forward im going to keep dosing with prime and looking for nitrate correct?

Hi G,

That’s good, it means you are at the beginning of the cycle. The nitrate hasn’t come from the ammonia being converted to nitrite then nitrate, it is there from the start. So when measuring your nitrate levels from here on out, 5 ppm is the baseline, as opposed to zero.

It sounds like you understand perfectly, you are waiting for nitrite to appear, it may take a week or two, or maybe, if you are unlucky, a little longer – but from here on out it’s just a patient waiting game. Don’t worry, it will be worth it!

Yahoo!! Im hoping that my fish survive . I know there are no guarentees but im crossing my fingers. Thanks for this, if i hadn’t seen this who knows what would have happened or if i continue with a hobby im starting due to not understanding the process and its rewards in the end. I will definitely check in when i see sum nitrite lol thanks for your time. Its much appreciated.

Good luck with it all G,

I’m looking forward to hearing your updates. If you have any questions regarding the cycle in the meantime, drop me a line in the comments here and I’ll do my best to help out.

Hello Ian, update… we have nitrite!! ???? . So ammonia is at 1.0 and nitrite at o.25. Ive also double dosed with prime. How long before i start to see nitrates? And when those levels reach 4 combined ill do a water change correct?. Do i add conditioner and bacteria stater in the new water? Or just use the prime in the new water? Thanks.

Hi G,

Woo! Progress! That’s awesome. It all sounds like it’s progressing nicely. Unfortunately, the answer on nitrates is it depends. It could be another week. It could be three. You’ll notice your nitrites spike before they go back down, so water changes might need to be done more frequently from here on out. I personally just use prime in the new water as a dechlorinator. You are correct on when to do the water change.

Good morning Ian,
Update… so ive noticed that my ammonia nitrite naver really rose above 2ppm. Im not sure if that a good thing or not. Im not sure if that was my spike bacause im now nothing my ammonia getting lower without me doing anything. My nitrite is also getting lower then it originally was. I assume thats all heading in the right direction but im confused with my nitrates. There are none! Why is that? Is that normal? Also, my tank water looks cloudy and wondering if water change is needed or will it clear on its own? Amonia @0.25ppm nitrite @0.55ppm tap nitrate @5.0ppm tank nitrate @5.0ppm i have still been dosing with the prime aswell. ????‍♀️ is my tank doing what its supposed to? Thanks.

Hello ian, so update.. sorry if this is a repeat i dont see the comment i left before … so i was wondering if my tank is still i good shape. I havent done anything besides prime dosing and testing with occasional feedings. Ive noticed my ammonia and nitite levels stayed within 2ppm or lower and have now started to decline but there is still no nitrate. Is there something wrong? Also the tank is cloudy and wondering if a water change is necessary. Thanks.

Hi again, G

It’s normal to experience cloudy water as your tank cycles, these are tiny bacteria that will go away on there own. However, if you are worried about just how cloudy the tank is getting, a water change won’t hurt – don’t forget the water conditioner.

It’s possible that your nitrate is going up, but it could be at 7ppm, which will look closer to 5ppm. This is the downside of test kits, you can only round them to the nearest reading on the chart, and you will have noticed that the gaps get bigger at higher levels.

As long as you are testing in daylight and following the test instructions exactly, you should be fine.

Hi Ian. This article is so incredibly helpful. Thank you so much! I just want to clarify… For the prime cycling, do you test daily and add the appropriate amount of prime everyday UNTIL the ammonia reaches 2 ppm and THEN do 50% water change? Or should I be doing water changes daily? Thanks!

Hi Katie,

Good question,

If you are using the prime route, you only need to do a water change once the ammonia reaches the level indicated. If you are doing the water change route, it’s daily water changes. Either way, daily or twice daily testing if your tank is a little overstocked, will reveal the course of action you need to take. Please let me know if I have not explained this well enough and I’ll attempt to clarify it further!

Hello Ian, i wanted to ask.. my uncle has 3 discs and he hadn’t cyled his tank. I taled him through the process and now ive noticed his discs fins turning black like they are burned. Any ideas as to why or whats going on?? Thanks

Hi G,

It could just be peppering which is natural and expected, google “discus peppering” for more info. Otherwise it could be fin damage from disease or physical damage. Either way, a test kit should reveal if the water has the right parameters or not and appropriate action should be taken to fix it. If the tank is indeed uncycled then that will lead to further complications and should be dealt with ASAP.

You are spot on with your thinking. Basically all fish in cycles are carried out in the same way – minimizing fish exposure to both ammonia and nitrite.

Hi Ian

I mistakenly bought my oranda fish before cycling the tank properly. My fish was not well, bottom hovering. My ammonia levels were a bit high so I did small water changes before choosing to do the prime route. I have been dosing daily with prime as your literature explained, the ammonia went down to almost trace and nitrites started to appear. My fish really perked up! Today I noticed my ammonia levels have spiked to 2ppm and my nitrites have declined. My fish is just hovering at the bottom again. Why is my cycle going backwards? I’m confused. More importantly I’m worried I’m poisoning my fish. Please help.

Hi Emma,

It’s hard to say, it could be the initial ammonia caused permanent damage and the effects are just now being seen.

Keeping water fresh is best, some readers here have found daily or twice daily water changes to really help. If your fish perked back up after the small water change, then perhaps this is the route you should continue.

On the ammonia route, prime converts ammonia to ammonium, which is still readable by many test kits, even though it’s considered harmless to fish. As long as you are following the instructions in this guide, it shouldn’t be an issue. However, in this instance, I do recommend going the water change route.

Hi Ian. I’ve found myself performing a sudden fish rescue and I had a question about seeding and what to expect.

Long story short, a neglected 30-gallon tank with 8 fish (small, mostly skirt tetras) became mine on an emergency basis. I was hoping to fire it up with the existing equipment and filter cartridges, but that turned out to be completely unusable. The substrate was also a big no-go. What I did manage to salvage: five fairly substantial aquatic plants that I’m hoping might have that beneficial bacteria colonizing them.

Should I expect these established plants to help a little, or a lot? It’s only been a couple of days, so I haven’t seen any ammonia or nitrites yet. I did see a small amount of nitrates but I think that may have just been my tap water. I’m going to be using the water change method, but I’m a bit nervous not knowing how big my ammonia spikes are going to be and whether or not the plants will make a difference.

Thanks for your time.

Hi Shea,

I would’t expect the plants to help much, beneficial bacteria congregates in porous surfaces, mostly the biomedia in the filter (such as ceramic rings) and the sponge with a little in the substrate. Plants are not particuarly porous and it’s unlikely they will house much beneficial bacteria at all.

It’s common for tapwater to contain up to 5 ppm of nitrates, so you are likely right that this came from your tap water. An easy way to test is to use your test kit on your tapwater before adding it to your tank.

Reducing feeding and keeping the tank clean will prevent ammonia from spiking outside of your control. It’s hard to say *how high* it will rise, all you can do is measure with your test kit and react accordingly.

Thanks for being awesome and giving these fish a second chance at life 🙂

Thank you, I’ll expect the cycling to be unmitigated by the plants and stay on high alert, then! I got a Seachem ammonia alert to stick to the side of the tank today, to use in addition to all the test strips.

I’m thinking of feeding them lightly every other day for a while, that’s what I’ve been doing so far and they seem OK with it. I’m pretty sure they were being way overfed prior to this. Does that sound reasonable?

I checked it from the tap like you said, and yes, the smidge of nitrates are just from that. Barely detectable.

I’ll do my best to keep it squeaky clean and give them the best chance possible, they are really neat and beautiful little critters who’ve been though a lot and they deserve to live! Thanks for providing this online resource and such clear instructions.

Thanks so much for the kind words. It means the world to me!

It sounds like you have your head around it. In the wild, fish wouldn’t be hand delivered a tasty meal every day – most aquarium fish can easily last a week without food.

Since you are doing a fish-in cycle, the only change I would recommend is swapping over to an aquarium test kit. Not only are these more accurate than test strips but considerably cheaper over the long term. For newcomers to the hobby, I generally recommend the API Master Test Kit – it’s affordable and lasts for years. Just make sure you read the test results in natural daylight – indoor lighting can make it harder to match the colors.

If you have any other questions around the cycling process, please comment here and I’ll do my best to offer assistance. Wishing you all the best through this cycle, I hope it all goes smoothly 🙂

I will see if I can order an API Master Test Kit off Amazon right now. I bought strips because they were familiar, but I can see that they’re going to run out before long. I thought the liquid test kits looked more expensive but I didn’t understand how long they could last – thanks for saving me some $$$! And I’ll read the results by the window in the sunlight, thanks for the tip.

I’ll keep my fingers crossed for smooth going, too! When I picked these fish up they looked terrible, I thought they were going to die on the way home. But after only a few minutes in clean conditioned water they bounced back and were swimming and respiring normally again. Right now they are zipping around, playing in the water current, foraging in the plants, and all that good fish stuff. I think they’re survivors, even if they have to go through some bumps in the process.

I’ve already found answers to many of my questions elsewhere on the FishLab blog, but if I think of anything else I need to know about cycling, I know who to ask! You take care now 🙂

It sounds like your new fish are going to be very happy. You might have to prepare yourself for the possibility that despite doing everything right, you still might lose some – that’s the nature of fish-in cycling and their previous conditions certainly won’t help. I have my fingers crossed they all pull through. Good luck Shea!

My apologies if this was already addressed, but I have. 55 gallon tank that has been going for over two months now. Everything has been fine, but about two weeks ago we noticed major fish death. We’ve performed many water changed and used Ammo lock plus other methods recommended. Yesterday we woke up to super cloudy water and did an 80% change. Things seemed to go okay and then the water was even cloudier this morning…so my husband did another water change. What are we doing wrong? We have 2 bettas and 4 tetras with some snails and small algae eaters. I know that is more fish per 5 gallons, but it’s way less than before and the water was never this cloudy or ammonia so high

Hi Liz,

If your ammonia is high, then it’s possible your cycle has crashed. There are many different things that could do this, so I won’t be able to help narrow this down.

Otherwise it’s an ammonia spike, which can occur when organic matter such as a dead fish, rotting plant or overfeeding occurs. I have seen this occur when substrate is not properly maintained and is moved around, freeing a whole bunch of waste that quickly breaks down into ammonia in the water column.

Your test kit should clue you in. If your nitrates are continuing to rise, then your cycle is fine and it’s an ammonia spike. If nitrates are static, your cycle has crashed and you will need to re-cycle your tank.

Hello – I have been doing a fish-in cycle with prime. My pH has been consistently staying at 6.0 (or lower). I’ve read that low pH can prevent the nitrifying bacteria from growing. Would you recommend doing a water change before ammonia is at 2.0 ppm to care for the pH?

Hi Andrea,

If you have soft water, then pH can be an issue. 6.0 is getting to the stage where it’s too acidic. I would attempt to maintain it using water changes, to get it back up but if you find it rapidly drops, then you might have to read up on “aquarium KH” it essentially buffers the pH and stops it from swinging.

Hi Ian,

After increasing and stabilizing my aquarium’s pH, I was able to successfully do a fish-in cycle using your instructions with water changes.

One day, nitrites appeared, and literally overnight, nitrates entered the equation and ammonia and nitrites were down at 0.

Thank you for posting this article and for taking the time to answer reader’s questions – my fish & I truly appreciate it!


Hi Andrea,

Congratulations! It’s your hard work that got you this far – well done. I’m so happy to hear that after the pH issue was sorted that it all went smoothly.

Hello again ian,
Update…. so I’ve been on this ride doing the fish in cycle. I believe I’ve reached the end of it but I’m not sure. As I stated before throught this process my ammonia and nitrite levels never rose above 4ppm. Today makes two days I’ve had 0 ammonia 0 nitrite with 10ppm of nitrate. Is it fair to say my tank is cycled? I’m hoping so lol. And if it is should the cloudiness go away on it’s own? Also should I still be using prime. I dont seem to see a ammonia spike after feedings. I also wanted to ask if seeing orange alge is normal if not how can I fix it. Thanks again for your time and help. Have a great day!

Hi G,

If your nitrate has been on an upwards trend, with ammonia and nitrite holding at zero, then it’s very likely your tank is cycled! If it’s cloudiness that is brought on by bacteria that are present in new tanks then it should clear up in a few weeks at most. If it doesn’t, then you’ll need to investigate as to whether it’s sediment or bacteria.

Off the top of my head, I can’t think of an orange algae, are you sure it isn’t something rotting?

Maybe brown alge. It’s all over my rock and decor. It’s not too bad but I hope it dont get out of control. I did lose a few fish in the process. And the last to go this morning was an angel fish that had fish rot I believe. He seemed to get better before getting worse. Maybe that was what was making my tank cloudy?. Welp I’m going to just continue with water changes and hopw the cycling process is over or nearly over. I’ll also continue to test just to make sure its established enough. Thanks.

If it’s brown algae, it *should* also go away on it’s own. Brown algae also often appears in new tanks before slowly disappearing. It sounds like you have a good plan there, keep me posted with how things go 🙂

Well, it’s been more than a week now and so far so good! The liquid master test kit has been an excellent thing to have, it really is much more precise. The test strips are kind of nice for a quick check in the morning so I at least know whether or not I can sit down and have a cup of coffee before doing fish maintenance, so they weren’t a total waste.

The rate at which the ammonia rises now seems to be tapering off and it’s hovering at under ~0.25 ppm (I’ve never let it get over 0.5 ppm, I’ve hauled many many of buckets of water, lol) and I’m starting to see the first hint of nitrites. I can see how this would be much easier with less fish bioload. 50% water changes every 12 – 24 hours has been kinda crazy! The fish are getting used to the python cleaner, it barely bothers them. I’ve already gone through almost 1/3 of a bottle of water conditioner.

The reason I mention this is so anyone reading comments here can see what they might be in for if they go over the recommended 1 fish per 10 gallons! Yikes! Also, mollies are eating machines – count one molly as like, ten fish!

Thanks to all the information on water quality from this guide and elsewhere on this blog, the tetras are even trying to breed. I had to buy an isolation compartment today to protect an eggy-looking female from being pestered to death by a mob of males. I’m going to reduce the amount of light and see if they’ll settle down. The plants turned dark green and sprouted new leaves, and the fish have also brightened in color – except the glass catfish, who is staying nice and clear. Hopefully he will survive this next part of the cycle as well!


Hi Shea,

Oh you poor thing, this has been quite an ordeal for you. I have to commend you for not giving up, especially with those water changes.

It sounds like you have gotten into a routine with even your fishies getting on board. Everything sounds positive, especially your breeding tetras – a big part of breeding fish is keeping water quality as clean as possible, so this is another sign you are doing everything right.

Hang in there 🙂

Thanks for the support! It’s not so bad, even though being the bucket brigade isn’t exactly fun, it’s rewarding, and luckily I have the time. I’m already itching to fill my entire living room with fish, maybe get my hands on a 75 or 90 gallon tank from the local secondhand fish store and do a nice big low-tech planted aquascape as an upgrade for these guys in a few months… I’m probably getting ahead of myself, ha.

I had no idea breeding fish were so kooky, the males bashed themselves against the outside of the isolation compartment for *eight hours* today without stopping, trying to reach their lady friend. They finally exhausted themselves and gave up, or maybe being in the darkness chilled them out. I’m really glad this annoyance is actually a reassuring sign.

Hanging in there 🙂

Oh breeding fish put on one fun show. It’s fascinating. Betta with their bubble nests is perhaps one of the most curious! But yeah, the males often give the females a good workout.

I can’t wait for the day you tell me it’s all over.

Well, I didn’t expect to have anything to say for at least another couple of weeks, but I’m a bit confused by the test results I’ve been getting over the past 4-5 days. I don’t know whether I’m making progress or if the cycle just stalled.

I started adding some Seachem Stability / bacteria in a bottle around when the nitrites appeared.

I’ve done only one water change recently (not long after I last posted) when the nitrites were about 0.5 ppm. I’ve been testing twice a day, and every time the ammonia and nitrites are lower than the last, and for 2 days now they’ve been either barely detectable or zero, even though I’ve started feeding the fish more generously.

However, I’m not seeing any nitrates, either. I notice the scale of the nitrate test is less sensitive – will it take a while to build up to a detectable amount? If the nitrate production is so far very tiny, is it possible the Stability BB and the plants (I have 10 plants now) are eating it up? Or do I just need to be patient?

Thank you, again, for your time.

Hi Shea,

If your nitrites are dipping, then nitrates should be almost a certainty. Can you double check that you are testing right as per the instructions? Also, are you testing under daylight – the ceiling lights inside can really throw the colors off.

Otherwise, everything sounds normal. I don’t think it has stalled, your nitrites or ammonia would be climbing if it had.

I’m 110% sure I’m performing the test right – I keep the booklet open and go step-by-step every time, using a timer, even though I have it memorized anyway. I did take several years of college lab sciences, so this isn’t my first test tube rodeo, either.

I’ve been checking it in the sun, both by the window and then standing outdoors, and I’ve also tried checking it indoors under some white fluorescent bulbs, and with a flashlight, trying to see a hint of orange under any conditions. Zip. But the nitrites were there, and now they’re all but gone, and I sure didn’t take them out… baffling.

I’ll have other people look as well next time, in case something is wrong with my color perception or something. Otherwise, I guess I’ll just wait. and keep testing until they show up. Good to know it doesn’t sound like a stall, at least.

Last possibility, and it’s also the very least likely, but it can happen – you may have a faulty nitrate test kit. I have only seen this happen a few times in my 30 years, so I do think this is the least likely potential.

If I was in your shoes, I would wait another week (with daily testing, of course) and see what it looks like then before acting further.

Hi Ian,

Thank you SO much for this great site! I have a rental property from which I had to evict tenants. The house was a despicable pigsty, and they *abandoned* six fish (who does that?) in a half-evaporated 55-ish (I am guessing) gallon tank. I live 4 hours away, so when I met the Sheriff to finally regain possession of the house, I was shocked. I grabbed a styro cooler from the nearest gas station plus some garbage bags, and at least knew to use the dirty and disgusting water they were in and not tap water. Seriously, they smoked so heavily (not that they were supposed to be smoking inside at all), that *the water itself* stank like cigarette smoke when I got home that evening. The learning curve has been almost all-consuming in the hours I am not at work.

They made it home, and I got online asap, so got some water conditioner and did two 50% water changes within a day, but sadly still lost 3 of the little guys. 🙁 I bought a 10 gal tank, then read about cycling, and thankfully all the generous aquarists out there like you kept me from making the mistake of plopping the remaining 3 in there, because there was a 6″ pleco (judging by the solid waste he generated, I shudder at the ammonia levels that he would have created), a 5″ Chinese Algae Eater, and a dwarf Gourami.

I kept up with twice daily water changes in the cooler until I got a test kit, and then rehomed the Pleco and CAE on Craigslist to a family with a large outdoor pond that is heated all year (yay!), and put the little Gourami in the 10 gallon tank while cycling.

I used two small bottles of Tetra-Safe, checked the pH, and had a heater, so thanks for the “Quick Cycling” tips post, which was super helpful. The second the ammonia was more than zero, I did a 25% water change, and only 2 needed in a week.

Happy to say I saw the first beautiful periwinkle color for nitrites after only a week, and am halfway through week 2, with two days of no ammonia or nitrites so far…hey, I should check for nitrates…can it be so soon? I just figured he’s a clean little guy, but what if? That would be so awesome!

Anyway, thank you for sharing your knowledge and expertise: it has kept these guys alive, and I know doubtless others as well, in addition to helping those of us brand new to the hobby start out the RIGHT way. I might have found my new hobby!

Pax et bonum,


Hi Sondra,

I am terribly sorry to hear about your predicament. Other people can be disgusting human beings 🙁

But you are an angel for attempting to save these fish, especially identifying the learning curve needed and sticking with it! I have so much respect for you as none of what you did here was easy.

To answer your question, absolutely you should check for nitrates. Truth be told, everyone experiences the cycling process somewhat differently and you may already be there!

Just be mindful that anything under 5ppm of nitrates *might* be already present in your tap water, so it’s worth testing your tapwater too, just to see what the baseline level is.

Thanks again for your great work 🙂

But I have my fingers crossed you are on the home stretch.

Hi again Ian,

Thank you for the kind words! I honestly could not have done anything else, however. 😉

I took your advice and tested my tap water, which did not show any nitrates; great idea to have a baseline and rule that out.

I did a 30% water change last night after 3 days showing no ammonia or nitrites, as the water was a bit cloudy. I think it’s from the substrate, because when I vacuumed that kicked up some cloudiness.

However, today again test results are: zero ammonia, zero nitrites, and zero nitrates. I am a bit puzzled, but am I on the right track thinking that (a) the water change would not have affected nitrates if they were present, because the bacteria live in the filter medium, and that (b) as long as there are is no ammonia, and no nitrates, there must be some level of nitrates or that wouldn’t be the case? Trying not to overthink here, so I will keep testing daily and just be patient.



A water change will lower your parameters. For example, a 30% water change would roughly lower these levels by 30% – if they were already barely readable, then it could have reduced them to zero.

To clarify, you don’t have zeolite or any other ammonia removing filter media in the tank do you? I only ask as beginners sometimes mistakenly put this is unaware they *want* ammonia to appear to kickstart the cycle.

If you are not, then it’s just a waiting game. Unfortunately, the first bit of fishkeeping is a test of patience.

Hi again Ian, and thanks for the reply.

I haven’t added anything to mitigate ammonia, and have just a regular Aqueon charcoal filter (QuietFlow CA10-2H) that came with the tank.

Readings today were still zero for Ammonia, Nitrites and Nitrates. I think he’s just maybe a super clean little fish, so I will just wait and keep testing daily!

Thank you so much for your time and care,

Hi Sondra, that certainly is odd. One thing is certain in fishkeeping: pee and poop. And, by association, ammonia.

If I was in your situation, I’d keep testing for another week or two, waiting for these to appear. It’s not a matter of if but when. Lucky, you seem like a very patient person. Good luck and if you have any other questions on the cycling process, please drop me a line here.

Thanks, Ian, you are right about fish output being inevitable!

I have a new puzzler, though. Yesterday: still zero ammonia, nitrites and nitrates.
Today: *barely* 0.25 ammonia, zero nitrites and zero nitrates. Well, I know “Gill” is doing his part;-)

However, I thought I would test pH and maybe I shouldn’t have, because the tank water is 6.0! I checked it again to be sure, with the same result. Then I checked my tap water to see if the test kit was actually working, and it’s 8.5. I remembered what you said about keeping the pH above 7, so I thought oh no, I hope the low pH didn’t kill the nitrifying beasties! And is it hurting Gill?

Then I remembered something about tannins decreasing pH, and I do have a piece of Mopani wood in the tank, which I pre-soaked and changed the water 3 x daily for 2 days before adding to the tank for that reason, and also the discoloration issue.

I’m fine with water changes when I see some ammonia and just hanging in there, but should I be concerned about the pH, or remove the wood? (Or just prescribe myself a chill pill? 😉


UPDATE same evening of 7-25-19: I did a 30% water change and it raised the pH to 6.6. I removed the wood, and put a ceramic coffee cup in for him to hide behind. I have a couple of plastic plants and it’s a calm household, so he should be ok for cover. (I have some Java Moss quarantined in a jar for later.) If you think I should do other things to raise the pH, I would appreciate your opinion; I don’t want to just knee-jerk and start adding things without knowing what I am doing. Thanks again!

Thanks for the update,

I’ll answer both of your comments here.

6.6 is probably as low as I would let it go for the cycling process. If your water change schedule keeps the pH at a constant semi constant (it will naturally drop over time, but slowly) then that is better than bouncing it around trying to reach a higher level. Stability is key if you have fish in your tank. Unless you soft water most fish keepers can balance pH just by performing water changes, assuming nothing else is causing them to drastically drop. I would only take action if your pH continues to rapidly drop now that you have removed the driftwood – if it does, and you can’t regulate it with regular water changes, then you might unfortunately have soft water.

Unfortunately, testing soft water requires another test kit that does not come in a master test kit. KH. For more info on KH, check out this guide – it doesn’t impact *most* fish keepers so I try not to mention it in my cycling guides, so as not to confuse beginners with another thing they have to learn.

But if you can avoid it, I recommend leaving it alone.

Hooray on reaching readable ammonia! Just note that it will get diluted if you do water changes, so don’t think you are going backwards if it dips after a water change.

Hi Ian,

Hooray, I finally have nitrates!! Today the readings were: 0 ammonia, 0.25 nitrites, and 0.5 nitrates!! I was so excited!

The pH was back down to 6.0 without the wood, so I did a 50% water change and that brought it up to 6.6. I’ll continue daily monitoring of everything, and keep in mind your information about soft water. I am studying your posts on KH and GH, as I need to learn that anyway. I think I’ll go ahead and order the test kit, too, because then I will have more data and advance another step on the beginner’s fish-keeping scale (pun intended.) ;-P

Thank you for seeing me through to nitrates! I will update when I cross the cycling finish line, but it’s very close.


Oh, I’m so relieved to hear that! Congratulations for making it to this point, I truly mean that. There is more waiting to be done, but at least you can be 100% confident you are on the right path.

For pH balancing, I’d focus on the KH article (so as not to confusethe issue too much, for pH it’s the more important of the two) It also might be worth checking in with a local fish store (try to avoid petco, petsmart or any other big box chain) – this fishstore should be using the same or similar water to you. If it *is* soft water, they will have a system already in place to deal with the pH swings. You could just copy that – it beats experimenting and trying to figure out how to best balance it on your own.

I would love an update when you reach the end, or if you have any other questions int he mean time. Wishing you all the best!

Hello again!

I thought I’d let you know that all my fish are doing super great, thanks in large part to your help and advice, and I’ve recently upgraded them to a 75 gallon. I simply popped my filter and everything else over into the new tank, so nothing changed but the glass box. No hiccups with the water chemistry. (Ammonia 0, Nitrites 0, pH ~7.5) They seem to enjoy the additional space and stability of the bigger tank very much.

I’ve also had some success with slowly bringing my water hardness down to more acceptable levels using driftwood and peat granules, AZ water comes out of the tap as more mineral than moisture. :/

I’ve built up more proper social groups for all my fish and now have a total 6 glass catfish and 12 skirt tetras. I might get 6 more catfish in a couple weeks, and then some snails a couple weeks after that. I think my molly is on the hyper-aggressive side so I don’t dare put anything in there that remotely resembles another molly in looks or behavior; even new sponges and rocks set him off something fierce. 😀 I also got them a ton of healthy plants from a cool LFS I found this week.

Since the tank/community is really only about 5 weeks old, a separate quarantine seemed like unnecessary stress for the newer fish. I figure everyone is on “probation” for many weeks to come, so the display tank basically *is* the quarantine. I picked out a few fish medicines to keep on hand so I can respond immediately if anyone does crop up with parasites, bacteria, or fungus, but I doubt I’ll need them if I keep their stress levels down.

I still haven’t gotten detectable nitrates with the API test liquid test or API strips, but I decided to quit worrying about it. I asked around forums and some people with extensive planted tank experience said my plants may be sucking up a lot of the ammonia and not to fret – with enough hungry plants the cycle can be completely or partially “silent”. I’ll probably buy a Salifert nitrate test eventually, I’m told they are more readable when your nitrate level is on the low side. Obviously with 19 fish there is ammonia being generated and I trust that it must be going somewhere!

Hi Shea,

Thanks so much for the update, it’s all thanks to your amazing work and research that your fish are doing great 🙂

Interesting feedback from the forums, I didn’t think your tank was heavily planted? I completely agree with the advice to push forward though, and especially on the salifert tests – I generally don’t recommend them for beginners as they need to be purchase individually and the costs can quickly add up.

Your comment on AZ water being more mineral that moisture cracked me up, that’s a great mental image!

It sounds like your aquarium is becoming really lively, with all the different fish – I’m sure it will be stunning once you can put this cycle behind you and sit back and really enjoy it! Although, I must warn you that if you are the type, you will forever be tinkering with it, adding a new plant here, a rock there… Before you know it, you’ll have 7 tanks. That’s what happened to me anyway.

I’m so relieved that everything appears to be going smoothly and I have my fingers crossed that you reach measurable levels of nitrate soon!

Yeah, they asked me to be really specific about the dimensions and types of plants and agreed that they were enough to potentially influence my results because of their growth rate and roots and whatever. They said if that was working to keep the toxins down so far, just keep adding plants to keep up with the load – so now I have floating plants, plants that I glued on logs, a stem plant forest, low-light carpet plants… lol. They also said it could possibly be a long, long time before I see nitrates but that in the meantime the fish should be perfectly safe, as long as the plants are maintained. Seems like voodoo to me, but ooookay.

The salifert tests are definitely a bit $$$, but only buying one isn’t so bad. I’m sure it’ll last a while. I think I can get it cheaper online, but my liquid gH/kH test just got lost in the mail, so I guess we’ll see if a nitrate test can actually make it to my door or not…

Funny that you say that about tinkering, today I was scrubbing and soaking some rocks and deciding how I’m going to arrange them. XD That’s the plus side of how chock full of minerals this state is, we already have an extensive rock collection laying around and it wasn’t hard to find something pretty (and inert, of course) to stick in the tank.

I’m already enjoying the heck out of it, my family and friends keep finding excuses to come over and see the tank. Despite the new-tank maintenance, overall they’re very relaxing and I love observing them – the TV has not been on much since they arrived.

Well, if one thing has come out of it, your aquarium will look absolutely stunning with all those plants. I hope you bought yourself a good aquascaping kit, you may have a jungle on your hands in a few months. I highly recommend taking a before and after photo, you’ll be amazed at just how different the aquarium looks once the plants fill out.

Ooooh lost mail is the worst. I hate it when you are excitedly waiting on something to add to a tank and then it just never comes. Unfortunately, a lot of the best stuff is available online – the local fish stores just can’t keep the same level of stock. I am currently in love with seed pods from Tannin Aquatics, they really add something different to my blackwater tank (if you can ever see one in real life, jump at the opportunity, blackwater tanks are stunning!)

I can imagine the extensive range of inert rocks you would have to choose from. I’m a little jealous. Due to the weight in shipping, good looking rocks are hard to come by and expensive. What do your family think when they see you washing rocks? Mine have long since come to terms with coming home and seeing a large chunk of driftwood sitting in boiling water on the stove.

You sure have come a long way from stumbling across neglected fish!

I was looking at a few different aquascaping kits with long scissors and tweezers and such. So far I’ve been pinching off old leaves and rubbing off algae spots with my fingers and I can see how that is going to get inefficient! Especially with Bernie (the molly) attacking my hand. Some gloves would be nice too, so I don’t have to hospital scrub every time. I think I bookmarked a glove recommendation you made on this blog.

Hey, I was actually thinking of ordering some sterculia pods, leaves, and driftwood from Tannin, they look like perfect catfish hidey holes. Some of their products also looked like they could be a more affordable way to keep my water hardness down after I run out of peat.

Blackwater tanks are beautiful! If ever I feel like hauling over RO/DI water from the the system at my grandmother’s house I’d like to try to pull off a small one someday. I hear the low pH comes with some extra challenges. For now I’ll stick to admiring their glory from afar. 🙂

Rock collecting is a family tradition spanning sixty or seventy years, so their main concern was looking over what I was doing to make sure I wasn’t running off with one of “their” rocks! As a kid, I remember how whenever we moved house we always had to make a trip with the moving truck full of nothing but rocks. My significant other was a bit perplexed by the rock scrubbing and the boiling wood, though. They’ll get used to it.

Maybe the neglected fish found me, I think I needed a hobby. 😀

My advice for the aquascaping kit would be to buy a cheap one that has a wide range of different tools. This will allow you to get a feel for what you use and what you don’t. Then as they fail, upgrade the ones you use to something nicer – proper stainless steel tools can be very expensive. I personally use the Seachem Auavitro but it can’t be bought online and it can only be found in local fish shops. I highly recommend the curved spring shears – you don’t have to manualy open them, after each cut, they spring back open. It’s such a minor feature but a dramatic quality of life improvement when you are trimming hundreds of plants, especially grass.

On the glove front, the atlas gloves are as good as they get. Keep in mind that if you sweat in them, which I imagine you might in AZ, they will smell a little funky, but it beats the toxic rubber smell the others gloves give. Flip em inside out to dry the lining. They are also the easiest to hold small fiddly items with, like aquascaping scissors – I am yet to find a better compromise on hand movement and protection.

On the tannin aquatic front, I have never used them solely as a way to reduce water hardness, I can’t comment on their effectiveness there. But fish seem to love them and interact with them a whole lot more than a plain substrate or grass. You can certainly find them cheaper (once you figure out what the actual name of the plant is) but to tannins credit, the ones they send are good quality and don’t appear to break down as quickly as other suppliers I have ordered from.

Ha, I love it. When I was a wee boy my my dad cut an agate (is that how you say that?) he found in half and it produced the most amazing crimson colors. I still have it sitting on my shelf to this day. I can see the appeal of rock collecting!

The rate you are adapting to this hobby, I fully expect you to be teaching me new things in a couple of months! It’s really good to see that, besides the minor cycling hiccup, this is all coming naturally to you!

Well, I’ll be darned – I thought my fish looked slightly lethargic this morning so I tested the water early, did a big water change before breakfast, skipped fish feeding time, and tested the water again this afternoon. I usually test the nitrites and ammonia first, and I got ruffled when I saw that after weeks of none, I was getting ~0.25 of each. I thought my cycle was starting all over again from scratch somehow and I was about ready to cry a lil bit at the thought.

But then I decided to test the nitrates and lo – at least 0.5 or 1.0! So now we’re having a happy fish party instead. 😀 I’m sure the little smidge of ammonia and nitrites will settle down soon. I’m going o send a picture of that orange test tube to everyone I know, ha!

I will definitely take your advice on the aquascaping tools, I’ll try to find a varied kit to start out. I know I prefer spring shears for dry land plants, I can see how they’d be extra useful underwater.

Oh, and I finally got my gH/kH test! It works great – I can see more precisely that I’ve gotten my gH down to under 250 – it comes out of the tap at like, 300 to 400 so I was very pleased. Even if the Tannin stuff doesn’t turn out to be very efficacious for my gH, I’m sure my fish will enjoy playing with it.

Woohoo nitrates! 😀 😀 😀 Thanks Ian!

‘Scuse me, I meant 5.0 or 10 ppm nitrates – I’ve been writing down fish water numbers so much that I’m losing my decimals. 🙂

Oh what a relief! That sounds hugely positive. Nitrate levels of 10 means your cycle is well on it’s way – It’s almost worth having a nitrate party after the ordeal you have been through!

Also, that’s good news on gH/KH test kit finally arriving. I know it wasn’t completely necessary, but it’s always good to get an idea of what is happening in your tank vs. what happens at water change.

I’m so happy to hear that after a few bumps, things are finally starting to look up 🙂

Hello Ian,

Your article is really helpful!

Unfortunately, I made the mistake of listening to a few store workers which did not give me any information or should I say accurate information and I found myself trying to learn this myself but found so many contracting things online.

I am still not 100% sure what I am doing so I am hoping that you can help walk me through my fish-in-cycling- I really appreciate it.

Okay, so I am going to make a long story short… I started out about a month and a half back- sadly I made the mistake of listening to Petsmart which told me that I could let the tank run for 24hrs, add API quick start then add my fish. I have 4 separate tanks with 4 betta fish so if you think that I can cycle with PRIME that would be the easiest for me but if I have to do water changes then I will do so.

I just want to mention that I had ONE of them for about 2.5 months. After reading your article- I think that I am technically going to have to start the oldest tank over so I will be cycling all of them. I made the mistake of keeping a mesh bag filled with White Diamond (CHEMICAL NEUTRALIZING CRYSTALS) because it said that it would help during the “break-in” period which I thought was referring to cycling. As your blog explains we should take this out which I did do that a few days ago- Am I correct in understanding that you say we should avoid using this during cycling?

I have had my 10 gallon with one of the bettas a little longer than the other 3- I thought that his tank was fully cycled but I actually had the ammonia crystals in it so right now I am not sure if its fully cycled. Now I am going to do a water test after I hear from you sometime today and see which way you would advise for me to go

Would the white crystal ammonia neutralizer give me false-positive readings?
Do I choose if I am going to cycle with EITHER water changes/OR prime because I have been doing both?
Should I fill up the 25% water I took out before reading your article or should I filled them back up with treated tap water? (right now I just have two of the tanks not filled up all the way because I wanted to hear from you first)

Let me know if I was clear about my situation! I thank you in advance for any help you can offer and will provide the results on the test kit once you give me the go-ahead.

Hi Dominique,

You are correct that you should avoid any “chemical filtration” that removes ammonia, while ammonia is harmful to fish, it’s essential to the cycle, so you need to keep it low in order to for the cycle to progress, not remove it completely. Sorry to hear that you will technically be starting from the beginning on this one.

It is still *possible* that despite this, the tank cycled, but don’t be surprised if it didn’t. Only a test kit will show you what is happening in your tank (I highly recommend a test kit over test strips) You are looking for:

Ammona = 0
Nitrite = 0
Nitrate = Over 5 (if it has been a while since your last water change)

If you have only just removed this media, then you may need to test for a few days to ensure ammonia or nitrite don’t rise. Your nitrates should always be rising in a cycled tank.

To answer your questions:

Yes, if the ammonia neutralizer is removing ammonia from your water and working correctly, then that could be the reason you are not detecting any ammonia. The only way to know for sure is to remove it.

Truth be told, whether you do a prime cycle or a water change cycle, you’ll be using a little of the other – sometimes ammonia or nitrite spikes and you need to quickly get it down, a water change is the quickest and most effective way of doing that.

I don’t understand the last question, I think you want to know: if you have removed the 25% tank water, you would replace it with treated tap water.

I hope this helps, please let me know if anything I have said needs clarifying!

Hey Ian!

I have tested the water the last few days. It’s readings in the 10 gallon tank they day before yesterday were 0ppm ammo, 5 nitrites and 5.0 nitrates yesterday it was 0ppm ammonia about 3-4 nitrites and over 0 but under 5 nitrates.

I am going to test tonight when I get home and update you- quick question. What why would I still be showing nitrites but no ammo and the nitrates are not rising? How would I dose with prime for no ammo but only nitrites.

The two smaller tanks have been up and running over a week and I am not showing any ammo so I haven’t used any prime or anything but I was doing frequent water changes which is probably why it hasn’t started to cycle. Should I be testing for nitrites as well or wait until the ammonia shows a reading? Also, do I need to dose with prime once I see a reading of .25 and above? Can you please explain that for me? Also, prime is a cap for 50 gallons- how do you measure what you would dose a 5 gallon tank?

Thanks Ian

Hi Dominique,

Truth be told, some people do experience the cycle slightly differently. Your ammonia eating bacteria may be at the stage where they are eating ammonia as quickly as it has been produced, yet your nitrite eating bacteria may not be quite at that stage yet.

You would dose prime the same as if it was ammonia only (per ppm) As for measuring it out, I use plastic pipettes, they allow you to easily measure out the correct amount (I never got the hang of measuring to the cap thread)

You can test for nitrites too, just to check what is happening, there is absolutely no harm in this! It will give you a better understanding of where each tank is at.

Please let me know if anything I have said needs clarification.

Hi Ian!

So I just tested the two tanks that I started cycling with the fish about 2 weeks ago and I am still getting a VERY low reading for ammo- its kind of hard to tell between 0 and .25 but I am seeing .25 for my 3 gallon and 0 for my 5 gallon. is that normal for 2 weeks? I tested for nitrites just in case and that is 0 as well… When should I start dosing with prime? Is it when the ammo gets to 1ppm and above or once it gets to .25 should I start now? Also, can you clarify on the prime dosage, the bottle says 1 cap for every 50 gallons but I don’t know how I would dose a 5 gallon and a 3 gallon….

My 10 gallon that has been cycling for a LONG time is reading 0 ammo- 0 nitrites and 0 nitrates. At one point I was reading ammo and about 2.0 nitrites and 5.0 nitrates now everything is at 0…

Any suggestions what I should do?
I also have questions about the tank I am cycling without fish but ill wait to hear back from you about this.

Hi Dominique,

I’d start dosing with prime now. Using a plastic pipette with fine readings will make it easiest to measure out the prime. I’d do 1/2 – 1 ml for both tanks.

I just want to confirm that you are using an aquarium test kit (not strips) and you are checking the results in natural daylight (indoor lighting can make the results incorrect) I would focus your efforts here, to make sure that you are working off correct results.

My understanding is that 10 gallon tank had the ammonia removing crystals in it? If so, day one started the day that you removed them, since it wasn’t technically cycling before.

Yes, that is correct I am using the API master test kit, not the strips. And the 10-gallon tank had the crystals in it, but they have been out for at least a month.

Now, since I am cycling with prime- should I add prime every single day? even if the tank is only reading .25 and at what point should I do a water change?

Thanks Ian!

I would add prime each day, doing a water change once a week (more frequent if levels begin to rapidly rise) the water change is still important as it adds trace minerals back to the water that fish use to stay healthy.

Hello Ian,
Sorry to be a bother but just to clarify you want me to dose with prime even when my ammo is showing between 0-.25? Can you please confirm again when I should be doing water changes? Should I wait until my ammo rises and I see nitrites? I don’t understand why its been 3 weeks and I am still barely seeing any ammo…

And as the tank goes that is in the process of being cycled did you say that I can just take the filter and gravel, put it in a new tank and not have to go through this process since the filter is already cycled?

Hi Dominique,

as per last comment:

Yes. If you read ammonia, you dose for it.

You do water changes once a week or more frequently if readings spike.

If the filter is rated for the new tank, and the beneficial bacteria is still alive, the cycle process will be instant or a few days at most.

I would suggest getting your water tested by your local fish store, just to make sure you are getting the same readings.

Wow! Thanks for all this very helpful info!

I have well water (pH in the mid 7s and up) with a water softener. I have a few taps in the house that dispense un-softened water.

Generally speaking, should I be using well water, or softened well water for my tank?

Hi Dave,

Glad you found the guide useful. If you can, my recommendation would be to go with the well-water, assuming it isn’t too hard and doesn’t have chemicals or high levels of nitrates (sometimes caused by run off) Using softened water can be a pain in the but as you try to manually adjust the water with remineralizers and buffers.

Hi Ian,

I believe the well water is fairly hard based on the fact that we needed a softener (don’t have a GH/KH test kit yet), and is showing zero nitrites and nitrates.

So I’ve been doing a cycle for over two weeks in a small (2.5 gal) tank with a single Betta, two plants, and an appropriately low-powered filter. Using well water (not softened).

My ammonia levels have never gone above .25ppm over these two weeks (0 nitrites and nitrates). pH has slowly increased from 7.5 to 8.2 over this period. Have done a couple of 25% water changes for good measure.

Do I just continue being patient and the ammonia level will eventually begin to increase, followed by nitrites, then nitrates?

Thanks again!

Hi Dave,

If you have hard or soft water, I highly recommend buying a KH +gH test kit (they usually come in the same pack, the API one does) this will let you know exactly what you are working with and will help to identify points of concern for the future (probably 90% of issues tanks arise due to water quality)

If you don’t have any media that removes ammonia or nitrite, then it sounds like you are on the right path. Unfortunately, the cycle can be slow and there is a lot of waiting. Also, keep in mind that some people experience the cycle slightly differently, you may find your nitrites never increase but nitrates do over time.

Do your tests in natural daylight (indoor lights make colors on the test kits look off) and keep doing what you are doing. It sounds like you are on the right path!

Okay so just to confirm start adding prime every day to the tanks reading .25 ammo – keep dosing every day and testing everyday, eventually I will see ammo rise which means I will need to add more prime? keep doing this until I see nitrites then dose accordingly adding the nitrites + ammo.

Im assuming eventually I will see nitrates… How will I know when the cycle is complete?

I also have a tank cycling that I want to put my girl betta in, right now she’s in a 1 gallon waiting for that to cycle. My question is what if I cycle that tank but I want to use a different tank since its really the filter were cycling can I just take the filter off the tank I am cycling now and use that or what would you suggest?

That’s correct. Try to space it out so that it’s at least 24 hours between doses.

You’ll know your cycle is complete when Ammonia is at 0, nitrites are at 0 and nitrates are constantly rising (these are then lowered with your weekly water change)

As long as the filter is rated for the larger tank, it shouldn’t make too much of a difference. Make sure you add the substrate too, if you use any, as some bacteria will live there too.

Hi Ian,
Thank you so much for the informative article. I have read it repeatedly, soaking up the information, but I still have some questions. The aquarium hobby is a treacherous path, as I have found out. I wish to tell you about my series of unfortunate events and encounters with fish people who seemingly have no idea of what they are talking about. I have made the mistake of listening to bad advice, as you will see in my (rather long) story, and I hope to hear your thoughts and recommendations in the end. I am hereby joining the club of fish keepers who though they had prepared fully before adding their fish…

I have a 180 L (47 G) aquarium, which has run for 6.5 weeks (46 days today). After seeking advice from articles online, visiting to two different pet stores, and having a chat with a goldfish seller, it seemed probable to cycle an aquarium in three weeks using bottled bacteria. I tried, and it failed in the end. I checked the water parameters many times during the three weeks at the pet store, (they used liquid testers) and was told that it was safe to add fish. I bought two high quality lion head Oranda goldfish with short tails (jumbo type), one male and one female, both yearlings, imported from China. I initially had sand substrate and some zebra snails in the tank, but I delivered the snails back and removed the sand to make things easier for myself. The two goldfishes are the only inhabitants for now.

Two weeks after getting the fish, the parameters turned bad. I used strips (highly recommended alternative to liquid tests, according to pet store), and saw a trace of nitrites. I brought a water sample with me to the pet store and had them check it with liquid tests. Oh yes, plenty nitrites there. I proceeded to do 50% water changes daily over a couple of days and had it checked again. Nitrites had risen even more. I repeated this process for a week, and saw that the nitrites went through the charts. I almost resigned and lost sleep because of worrying about my fish. The pet store worker was convinced that the nitrate cycle went like this: nitrite to nitrate to ammonia, so according to him, ammonia was not important to check for yet. This made no sense to me, so I asked him to check the ammonia anyway. It showed no ammonia, but the nitrites were as high as they could be. My conclusion is that the ammonia spike was finished and processed at that point. I stopped going to the pet store and bought a liquid test kit myself.

I test the water daily, and for the last three weeks, there has been no trace of ammonia, only nitrites. I have done 50% water changes two times a day to keep the nitrites down to between 0.2 and 0.5. The nitrites are not rising as much anymore, and the nitrates are present as well, but not in great amounts. I had another chat with the goldfish seller and he recommended the Takazumi Nitrifix liquid, which converts ammonia and nitrites into nitrate in the end, basically doing the job FOR the beneficial bacteria. I noticed that the nitrites almost completely disappeared with this, but only when I used it. During this time, thinking the nitrogen cycle was almost complete with very low levels of nitrite, I did a total of 30% water change daily. Then I noticed that if I stopped, the nitrites came back again the following day. It was not a permanent solution, so stopped using it (used it for 1.5 weeks in total). Thus, my questions are: When will the nitrites finally reach zero? And more importantly, how much nitrites need to be present for the bacteria to keep multiplying? Did I do more damage than good with the Nitrifix, considering it seemingly consumed the «food» of the nitrifying bacteria before they could get to it? Nitrate is being produced, so there is activity on that part, but I am slowly reaching my wits’ end by not knowing if what I am doing is right or not.

The tank is now bare-bottomed with plenty of plants: big Java ferns, Anubias and Pothos. The roots of the Pothos stick down in the water to extract nitrates. Filtration consists of two XL sponge filters and a Ziss Bubble Bio Filter (a liquid filter, new on the market). In addition to this, I have an air stone. Everything runs on two Eheim air pumps 400. This should be plenty filtration, right? All four items produce bubbles to oxygenate. To regulate the KH, I put two cuttlefish bones on the bottom of the tank. I did not use the Nitrifix liquid last night, and the nitrite was 0.06 before I went to bed. This morning the values were as follows: NO3 = 10 (hooray), NO2 = 0.5 (oh noo), NH3 = 0, GH = 5, KH = 5, pH = 7.5, Cl = 0. Temperature = 23-24 Celsius. I am not using a heater. I performed around 60% water change after reading the values. All values are very stable, except for the nitrites. The nitrates are low (under 10) most likely because of all the water changes. I tried to wait 36 hours before water change and then the nitrate reaches 15, but the nitrites would be dangerously high (= 0.7). I hand feed the fishes a small amount of gel food (Repashy soilent green) in the morning, and I remove all debris and poop from the bottom of the tank twice a day, thus nothing is decaying. I always use dechlorinated water when performing water changes, even if our water contains no chlorine anyways, so this should not be a factor for the bacteria.

But guess what, my gentle giant goldfish are still alive. No gasping for air, no burns, no buoyancy problems, no lack of appetite, no nothing. I cannot believe it, considering that I have put them through both the ammonia spike and the nitrite spike due to my lack of knowledge. To top off the story, my male goldfish was so eager to eat one morning that he managed to dislocate his upper jaw a little, so we are getting a visit from a fish veterinarian this upcoming week. The moral of this story is follow your gut feeling and spend time finding the right people to talk with before doing anything. I have been so naïve, thinking that pet stores would give me the correct information. But now I am unfortunately in a situation of fish-in cycle that has been going on for 6.5 weeks and would very much like your thoughts and advice on this matter.

Kind regards, Oddrun.

Hi Oddrun,

I’m terribly sorry to hear about your ordeal. Unfortunately, there is a lot of misinformation in this hobby and it can make it difficult to correctly identify the initial steps you need to take.

I assume you are located elsewhere in the world? I am unfamiliar with Nitrifix, it isn’t a product that I have come across in the United States. However, your thoughts would be correct here. If it does the work *for* the bacteria, then you are essentially depriving the bacteria of food, which would slow down the cycle. While you don’t want high levels of ammonia and nitrites, *some* amount needs to be there. Because we want to keep these levels low, so they don’t harm the fish, this process can be very slow and the only real solution is to measure and wait it out, only reacting if any readings seem abnormally high. As for when the cycle will complete, it’s possible you did slow it down by using nitrifix, but I have seen some tanks take 2-3 months to cycle.

A quick tip on the test kit, if you take the results and compare the colors in natural daylight, you’ll get far more accurate results. Indoor lighting can make the colors look off, and can lead to an incorrect match. It sounds like you are all over this, but I just wanted to clarify to make sure you are getting the right results.

The good news here is that it sounds like you are doing everything right. The sponges should provide an abundance of biofiltration for that tank, and things seem to be progressing, but slowly. You are certainly on the right track and I’m sorry to hear there were some speed bumps before you got here. Just keep doing what you are doing and your tank will eventually be cycled – Unfortunately, it’s just a waiting game here.

Hang in there, things will get easier! Feel free to drop me a line here if you have any further questions.

Hi again!

Thank you for your quick, kind and understanding reply. I really appreciate it. Your response has calmed me down a bit.

You are correct that I am located elsewhere; I am Norwegian but I live in the Netherlands, Europe. 🙂 Nitrifix (brand Takazumi) is an Asian product recommended by the goldfish seller. He said it would fix my nitrite problems, but failed to mention that it is only temporary. I think I will save the product and use it in emergencies only.

I have a question regarding what you say about nitrite and only react if it gets abnormally high. How high is abnormally high? Is there a certain ppm I should aim for? Example: I checked nitrite and nitrate this morning and I got the following readings: NO3 = 10, NO2 = 0.6. The fact that I have 10 nitrate after two 50 % (a total of 100 %) water changes yesterday is progress. That means I have 10 nitrate two days in a row with huge water changes in between. Hooray! Back to nitrite, the readings showed approximately 0.6 (perhaps 0.7), is that considered abnormally high? After reading the result, I did a 40 % water change because I do not know what level of nitrite is tolerable. Should it be around 0.5? 0.3? I have no idea. I use the JBL test kit and the nitrite readings on the chart stops at 1 ppm. To address your other thought, yes, I use daylight to read the colours. I am happy you mention that since it makes a big difference on the readings.

A new treacherous example popped up since yesterday. I reached out to a profiled fish keeper on YouTube just to see what he had to say about my nitrite and fish-in cycle. His response blew my mind. He said, quote: “If you’re not seeing ammonia, let it be. As long as the *nitrites* don’t get above 4 or 5 ppm, you’ll be fine. Ammonia is what you need to worry about. At the rate you’re doing water changes, the tank will never settle in.” According to him, nitrites are not much to worry about, but that contradicts everything I know about nitrite. 4-5 ppm nitrite has to be beyond abnormally high, right? Also, considering that my test kit stops reading at 1ppm, it will be rather difficult to achieve.

Another question I have is regarding adding new fish. I bought the third and last goldfish for my tank two weeks ago, but I have not picked it up from the goldfish seller yet. He put it in quarantine because the fish was just delivered to him from China. I told him that I would pick it up after the tank is fully cycled. What are your thoughts on this? Is it better to add the fish before the tank is fully cycled or should I wait? I assume that the ammonia and nitrite will get another small spike when adding a third fish to the system. Everywhere I read it says I should wait a certain amount of time before adding more fish, to let the bacteria adjust. If I wait until after the cycle has finished, then what are they adjusting to? I thought the bacteria adjusted after the amount of ammonia is being produced in the tank? So waiting for three days or a month after the tank is cycled, how does that make a difference? I will not add the last fish yet if that is not recommended, of course. But, I am curious to hear your thoughts on this matter as well. 🙂

Those are some good questions!

It sounds like the nitrifix would be a good emergency product to keep on hand just in case. I hope you never need to use it as things would be pretty disastrous for the need to arise.

So “abnormally high” depends on the technique you are using. Since seachem prime neutralizes the harmful substances, you could have up to 5ppm of nitrite (assuming no ammonia) in your tank and it would be harmless. Of course, lower is better but this is talking about extremes.

If you are relying on water changes, 0.5-1 would be as high as you want it to go (extremes again, under 0.5 is ideal). When it reaches this, you would immediately perform a water change to get it back down.

Nitrate is more harmless, in a non-planted tank, you would expect it to rise to no more than 40 ppm (again, extremes) with the goal of getting it back under 10 with your weekly water change.

As for this youtube expert, speak to 10 different “experts” and you’ll get 10 different replies. It’s an interesting field in that there is no universally agreed upon correct way to do things and I try to distance myself from these debates. I disagree with him that your tank will never settle – that thought defies logic. Let’s say your tank produces a constant 0.5 ppm and never rises higher. Your beneficial bacteria are going to adapt to that 0.5 ppm and it will then read zero. The idea here is that as the beneficial bacteria grow, the spacing between the water changes widens further and further. While the results may still read “0.5” it is now taking more days for it to exceed that, which is a sign of the bacteria colony growing.

I also disagree that nitrites are not harmful. Of course, fish show different signs of stress (or even none) according to their sensitivity, but just because a fish doesn’t die doesn’t mean that it’s thriving. Anecdotally, I have seen fish that had a terrible start in life (ammonia and nitrite elevation) live lives half as long as otherwise would have been expected. In a fish-in cycle, it is in my opinion that it’s best to go slow. The safety of your fish is the primary concern and to do that, you want to keep these chemicals as low as possible. Sure, 5 ppm of nitrite will make the cycle proceed faster but that’s not what a fish-in cycle is about. There are numerous studies on nitrite toxicity in freshwater fish. For example, Rainbow Trout exposed to 0.5 ppm of nitrite for 24 hours suffered a 55% mortality rate. Of course, this will vary according to fish and sensitivity, but in my opinion, nitrite is absolutely dangerous and I would never recommend anyone do a fish-in cycle with 5ppm of nitrite.

On the add a fish, it’s a judgement call as to whether or not you add it now or later. For beginners, I generally recommend adding it *after* the cycle, as this allows them to work on understanding readings, how the cycle works and all the basics. This way, when they add a new fish, they are fully prepared for any spike or adjustment that occurs. It also means the new fish will be exposed to the least amount of ammonia and nitrite possible and if there is a sudden spike, you can be sure it’s the addition of this new fish that caused it (the cycle can be difficult enough as it is to track without these complications)

I hope that helps!

Thank you again for your informative and thorough answers. It is a pleasure to converse with someone who knows what they are talking about.

I will aim to stay right below 0.5 ppm nitrite. Between the water changes it now creeps up to around 0.6-0.7 ppm, which is within the limits you spoke of. Just now, I measured 0.6 ppm nitrite, which I reduced to 0.4 ppm with a 45% water change. I’ll try to keep it there. Have I understood you correctly then? The nitrite should show some reduction soon, since I measure a small increase in nitrate every morning now. This morning I measured close to 15 ppm nitrate, compared to around 10 ppm 24 hour earlier, with the same big water changes in between.

When it comes to advice from the “professional” on YouTube, I agree with your reasoning. The fish’ well being is what’s most important. Then it doesn’t matter if it takes three months and two water changes a day to cycle the tank, should you find yourself in a situation of having to perform a fish-in cycle. I have learned that it’s best to cross-check the information you find, do your research, and use sound logic to find the right answer and solution to your questions. Hard lesson learned. I hope people will avoid making the same mistakes I did.

As for adding the final fish, I will wait until the tank is fully cycled. Preventing the fish from experiencing unnecessary hightened levels of nitrite is the kindest option.

I will definitely reach out to you again if there are new hurdles coming up. If you want, I can keep you posted on the development. Every successful ending deserves to be shared with the people helping you get there. Thank you so much for your help so far!

Kind regards,

Hi again, Oddrun,

What you are doing here is spot on. It’s now just a matter of daily testing and reacting according to what your test results show.

The nitrite will show a reduction soon, especially as your nitrate levels start to rise quicker and quicker. If you are already noticing the nitrate spike, then your cycle should be done sooner rather than later. Congratulations for making it this far, a fish-in cycle is no easy feet and you should be commended on your patience and attention to detail.

It sounds like you are well on the path to success. I’ll be excited for you when the tank is finally cycled, so please reach out again when you reach the goal. Or earlier if you have any other hiccups and I’ll try to help.

Wishing you all the best!