Last update: November 12, 2022

Brown Algae in Fish Tank & How to Get Rid of It

It happens all of a sudden…

Without warning…

One day your tank is crystal clear. The next it is a brown slimy mess.

If you have ever owned a fish tank then you will know it all too well.

I am talking about, of course, brown algae.

That dreaded brown, slimy substance that, if left unchecked, can take over your entire aquarium.

So how do you get rid of brown algae?

Well, I’m glad you asked. Today I am going to teach you everything you need to know to win your brown algae battle.

Fun fact! Brown algae isn’t actually algae at all…

If you use the same removal methods on brown algae as you would on other algaes, you are destined for failure.

This is because brown algae is actually a tiny little animal called a diatom.[1]

This creature is sooooo small that it cannot be seen without a microscope.

Brown algae diatoms viewed under a microscope
© Olympusman,

You are probably thinking:

If I need a microscope to see it, then why is brown algae clearly visible in my tank?

Well, “brown algae” is actually made up of billions of tiny interlocked diatoms.

So if you wanted to get technical, brown algae is actually a bacterial colony – not that it makes you feel any better about the brown film that is covering the inside of your tank.

How do you identify brown algae?

Brown algae covering aquarium glass and plants

Brown algae forms in soft brown clumpy patches. Brown algae is a terrible swimmer and instead prefers to attach itself to a stable surface in your tank such as the glass, substrate or even plants and decorations.

The soft slimy structure can easily be removed by lightly rubbing it with your finger.

What causes brown algae to appear in your tank?

Betta in tank with brown algae coating fake plants and ornaments

Consider it a rite of passage – brown algae often appears when cycling and maturing a new tank. Brown algae is something that nearly every rookie tank owner has to endure, and the problem generally resolves itself within a few months.

But that’s not the only time it pops up…

Brown algae is a natural part of your ecosystem. But if your brown algae is growing out of control then you may be encouraging its growth with the following:

1. Silicate in the water

Silicates are considered to be the number one cause of brown algae blooms. To put it simply, silicates are a diatom’s favorite food. They find it delicious and will happily thrive and reproduce in any tank that is high in silicates.

Potential sources of silicate in your tank:

  • Tap water and well water
  • Salt mix
  • Live rocks
  • Live sand

Anecdotal evidence suggests that play sand, blasting sand and other silica-based sand mixes may also cause silicates to “leech” into the water.[1]

2. Presence of Nitrates

If there are no more silicates left, brown algae can also survive on nitrates in the water.

Potential sources of nitrates in your tank:

  • Tap water and well water
  • Plant fertilizers (nitrate is often a main ingredient
  • Fish food
  • Decaying plant matter
  • Fish poop

3. Presence of phosphates

Potential sources of phosphates in your tank:

The most common source of phosphates comes from wastes as they are broken down in your aquarium.

  • Uneaten fish food
  • Plant decay
  • Dead algae
  • Fish poop
  • Dead fish
  • KH and pH Buffers
  • Tap water and well water

Brown algae doesn’t care whether your aquarium has freshwater or saltwater – if your aquarium has a good source of the above nutrients then you are basically laying out a welcome mat for it.

4. Poor lighting

It is also commonly thought that low light levels can contribute to a brown algae outbreak.

Whether this is true or not is up for debate.

Because “brown algae” isn’t an algae but diatoms, lighting isn’t thought to be a major contributing factor to its appearance….

As long as the water has silicates, brown algae is just as happy to grow in a dimly lit tank as it is in a bright one.[1]

However, many publications continue to list limited light as a cause for brown algae.[1]

Can brown algae harm your fish?

Fish swimming next to brown algae in tank
Credit: u/PapercutsAndTaffy

No. Brown algae is considered to be harmless to your fish – it won’t kill them.

In fact, brown algae could leave your fish healthier than ever!

You see, the diatoms that make up brown algae actually consume CO2. They then release pure oxygen, which increases the dissolved oxygen levels in your tank.

All aquarium owners know the importance of oxygenated water!

Fish that seem more lively with brown algae in the tank may be a clue that the oxygen levels in your tank are too low.

For the most part, fish don’t care about brown algae and will happily swim in a tank that has a good coating of the brown gunk.

But I have bad news for those of you with reef tanks or planted tanks…

Brown algae isn’t as forgiving to your fish’s environment. If you notice brown algae coating your plants or coral, don’t leave it sitting too long.

While brown algae won’t kill your plants and corals just by coating it, it will compete for nutrients and block out sunlight – which can result in death of your beloved aquarium plants.

How to physically remove brown algae from everything

Hand wiping down brown algae on aquarium glass with sponge

Dealing with brown algae isn’t difficult. In most cases brown algae problems clear up on their own.

If you are sick to death of staring at the brown slime, follow the steps below to get your brown algae problem under control without causing harm to your tank.

Remember to thoroughly wash your hands and remove any jewelry before placing your hands inside your fish tank.

How to remove brown algae from the glass of your fish tank

It doesn’t matter whether your fish tank is glass or acrylic, any brown algae that coats the walls of your aquarium can simply be wiped away.

The trick here is to use a single smooth wiping motion, from top to bottom. By doing this, you are “scooping” so that as little brown algae as possible floats off into the water of your tank.

I personally have the most success with a small squeegee (like this one) for swiping away the brown algae on the front of my tank.

However, a simple cloth/sponge and a steady arm can work just as well.

How to remove brown algae from your substrate

The technique needed to remove brown algae will be determined by what substrate sits at the bottom of your tank – pebbles, gravel or sand.

Pebble/gravel substrate

While larger pebbles can be removed and cleaned separately, smaller pebbles and gravel are best taken care of with a siphon vac.

Make sure that you only vac the top layer of gravel, otherwise you can remove all of the beneficial bacteria in your tank – which could actually make your brown algae problem worse.

If you find that the brown algae is gripping tight, you can remove the top layer of gravel/pebbles and wash them separately before returning them to your tank.

Sand substrate

Brown algae will only rest on the top layer of your sand.

It can easily be removed by gabbing your fish net and gently running it along the surface of the sand.

The idea here is to remove the top film of brown algae while leaving as much sand as possible behind.

Simply scoop out the brown slime and repeat until you have removed as much of the algae as possible.

Those of you with a vacuum may carefully attempt to suck up the top layer of algae from the sand.

If you find that the brown sludge won’t budge, tape a pointed object to the tip of your vac like so…

vacuuming brown algae off sand trick

The tip will help separate the brown algae from the sand, leaving the vacuum free to suck it up.

How to remove algae from live objects like plants and coral

Care is the name of the game here. These sensitive objects require a gentle touch.


Grab your turkey baster and use it to blow water over your coral. The brown algae should disperse through the water, where it will then be picked up by your filter.


Gently wipe down any surfaces of the plant with a soft sponge; the brown algae should lift right off and your filter will take care of the rest.

How to remove brown algae from fake plants, fake rocks and other ornaments

Fake plants, decorative rocks and other ornaments should be removed from the tank and cleaned separately.

Once removed from the tank, place ornaments in a bleach solution:

  • Imperial: ½ cup of bleach per gallon of water.
  • Metric: 4 tablespoons of bleach per litre of water.

Soak for 10-20 minutes until you see the brown algae floating to the surface.

Remove the ornaments from the bleach solution and rub them down with a soft sponge under running water before rinsing thoroughly.

Ornaments – scrub clean in a mild bleach solution. Rinse thoroughly.

How to stop brown algae from making a comeback!

Brown algae on sand substrate in tank

Once you have removed all the brown algae from your tank, you now want to ensure that the environment in your tank isn’t encouraging it to make a comeback.

Like a retired rock star in his 60s who is short on cash, brown algae can spring up out of nowhere again, even after you have removed it.

If you are an expert you can skip this section; you will likely have an appropriate routine in place to maintain the best water quality.

But if you are new to aquariums, then the following tips can help prevent brown algae from returning.

Step 1: Adequate filtration

I know it may seem obvious, but I have seen it time and time again – beginner hobbyists using the wrong filter for their tank.

Adequate filtration set-up plays a vital role in a healthy fish tank. Check your filter to ensure that it is rated for the gallon/litre capacity of your aquarium.

While you’re at it, make sure your filter is clean and functioning properly.

If nitrates (from dead organisms and uneaten food) are a problem, you may also want to invest in a protein skimmer, which also helps prevent algae build-up and assists with keeping your water crystal clear.

Okay, so you have adequate filtration? Good. Onto the next step!

Step 2: Water Movement

In order to discourage brown algae diatoms, you need water movement.

You see, diatoms are terrible swimmers. This is why they like to bulk up and coat everything in your tank.

If the water is moving, diatoms have difficulty clumping together and anchoring themselves onto the surfaces in your tank.

The added water movement will also ensure that all the water in your tank is filtered, instead of just a portion of it.

Water movement can be achieved by using a powerhead or current maker.

With the water flowing, it’s time to move onto the next step.

Step 3: Water change

Water changing should already be part of your aquarium maintenance routine.

However, the water you are using may actually be a major contributor to brown algae.

Tap water and well water can have high concentrations of the nutrients that brown algae loves to eat.

So how do you prevent your water change from encouraging the growth of brown algae?

Your best bet is to use reverse osmosis (RO) water, which has had its impurities removed. RO water is also known as DI water.

While you can buy RO water in bottles, the cost quickly adds up.

It’s cheaper to “make” it yourself using a Reverse Osmosis filter system.

Step 4: Don’t overfeed

You see that excess food that falls to the substrate of your tank?

If not taken care of, that fish food will rot, releasing nutrients that brown algae loves.

Step 5: Avoid all sources of silicates

Since silicates are considered to be a major contributor to brown algae blooms, you want to avoid introducing them to your tank when possible.

Every time you add something new to your tank, check the ingredients.

Live sand, salt mix and silica sand may all contribute to an abundance of silicates in your water. And when that happens, it’s brown algae time!

Tried everything and still can’t get rid of brown algae in your tank?

If you have tried all of the above and still can’t get rid of the brown menace, then it’s time to call in the big guns.

1. Filter Media

You can use filter media to strain the brown algae’s food source, starving it out.

phosguard to remove silicates from water to prevent brown algae

Filter medias like Phosguard contain aluminum dioxide. Silicate and phosphate gets absorbed onto the surface of Phosguard and is then removed from the water.

2. Dosing

Reduce phosphates and nitrates through dosing with NO3:PO4-X, a chemical designed to reduce phosphates and nitrates, in reef and marine tanks.

Dosing with n03:po4-x to remove phosphates, nitrates and silicates

To put it simply, NO3:PO4-X encourages the growth of nutrient-reducing bacteria (the good bacteria that naturally exists in your tank). This bacteria eats the same food sources as the brown algae, starving it out.

Other aquarium hobbyists report having success by dosing with vodka. [1]

Introduce fish and critters that feed on brown algae

Alternatively, you can introduce fish to your environment that actually enjoy the taste of algae.

This should only be done as a last resort.

Adding a live creature to solve your algae problem comes with its own set of challenges, including:

  • Does it play nice with your other fish?
  • Will it survive in your ecosystem?
  • Will it eat brown algae or your fish food?
  • What do you feed it once the algae has gone?
  • How do you care for it?

If you still want to go ahead and introduce a brown algae eater to your aquarium, then you can choose from the following list:

3. Freshwater algae eaters

  • Amano shrimp
  • Ramshorn snails
  • Nerite snails
  • Twig catfish
  • Bristlenose pleco
  • Siamese algae eater
  • Malaysian trumpet snail

Saltwater algae eaters

  • Blennies
  • Trochus snail
  • Kole tang
  • Emerald crab
  • Tangs


As you can see, brown algae isn’t something to fear. It is easy to get rid of brown algae and it also provides a visual warning sign that the nutrients in your tank are out of balance.

How do you take care of brown algae? Share your tips 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 (60)

Hi Don,

No, I have never used these chemicals to get rid of brown algae. In my opinion, chemicals should be used as a last resort. In most instances, brown algae will go away on it’s own.

Hi Dianne,

Unfortuantely, no. UV sterlizers are best suited for free-floating algae. Anything that is stuck to the surface of your tank, like brown algae, won’t be treated.

Thanks for the great article. I had fish for many many years and brown algae never took over my fish tank until now. New place and white sand. I know the water quality at my home is very hard I treat it and scrub all the decorations and somehow I can’t keep fish alive. I was thinking either getting rid of the expensive ciclid sand or growing moss bed . What are your thoughts ?

Hi Marlene,

It sounds like you need to test your water parameters if you can’t keep your fish alive – it sounds like something is amiss. The appearance of brown algae alone won’t kill your fish. What are your results on your aquarium test kit?

Hey there! I’m having exactly the same problem. I have had fish for years! I set up a tank, it did great during the first cycles. I added a cichlid a few weeks later. He did great for about a month. Brown algae started to appear and he was spastic. I thought the nitrate level was too high so I did a partial water change and changed the carbon bag, that didn’t help. The fish ended up dying about a week later. I haven’t put a new fish in it, because this brown algae is just continuing to grow.
I was wondering if you were using the bug bites for cichlids food? I noticed whatever the fish didn’t eat was growing almost a white fuzz all around the left over nugget and I’ve never seen that before. I know some foods carry a heavier filter load than others and I’ve not used that type of food before. I’ve aleays used fzn blood worms or flakes. Think I’m going to double up on the filteration and add a couple shrimp and run another test to check the levels.

I am having a Arowana fish in my tank. Does tanning lights help to build more brown algaes? Do i need to switch it off my lights?

Hi Wilson.

When you say tanning lights, Do you mean lights that help highlight the color of your fish? The UVA/UVB ones? Upfront: I don’t have a whole lot of experience with these, but I don’t see how it could differ to regular aquarium light use.

My 55 gal planted aquarium is loosing the battle to brown algae, I tried introducing some Otos, but they can ‘t keep up. I just introduced Phosguard, but how long do I have to wait until I know it’s working?

Hi Huklab,

Have you tested to confirm that phosphate is the actual problem? No point adding a phosphate remover if it isn’t. Testing is once again the solution to determining if the Phosguard is working – you’ll notice your phosphate levels decreasing. Phosguard absorbs fast and you should notice a dip in a few hours, depending on how dramatic your levels are. To me it sounds like you don’t have a phosphate test. Grab one of those first, and test your other water parameters while you are at it. Otherwise anything you do past this point is just guessing.

You suggested a bleach solution for the decorations. My concern is how can I be sure I’ve got all the bleach rinsed off before putting it back in the aquarium? I don’t want to accidentally kill any fish. Also, is there a specific type of bleach to use or just regular bleach like you use in the washing machine? I’ve already scrubbed the decorations once, vacuumed the gravel, and did a water change, but the brown algae is returning.
Thanks for your help.

Hi Rhonda,

Unless you have a planted tank, I’d personally wait a few weeks to see if it goes away on it’s own. It often does. As for the bleach, concentrated clorox will do, the stuff without fragrances or additives. As for how long to rinse it, under running water for a minute or so before rinsing in freshwater (treated with dechlorinator for a minute) would be more than enough. If you are really concerned, you can substitute for H202, which will literally break down into hydrogen and oxygen in your tank (same stuff as water) instead. But countless others have no issues with bleach dips – in fact, it’s commonly used to quarantine plants before adding them to the tank.

Hi Roy,

Thanks so much for pointing this out. It looks like my spell checker got the better of me on this one! I have fixed this out. Thanks again for your help!

How long does brown algae take to go away on it’s own?
I have had it for a few weeks now and it just seems to be getting worse!
I have taken everything out and scrubbed it, and reduced the amount i feed the fish.

Hi Laura,

If it’s a new tank, it can take as long as a month or two. This is assuming you are not dosing something in your tank that it is using as a “food” otherwise the only way it will stop if if you deprive it of the nutrients it is feeding off.

You might want to add young panda loaches to your list of effective brown algae eaters. I have 3 panda loaches, 6 Nerite snails, and 4 otocinclus and in my fairly new tank the pandas are the best cleaners of brown algae. They never stop eating the brown algae.

Hi Sam,

Thanks for the sharing, I’ll certainly add this the next time I update the article. I had no idea panda loaches devour brown algae!

As a newbie tank owner, building up (we have 6 rasboras, which we have had for a week, and a betta, which we’ve had for 2, and are getting a few more more rasboras and a cory for our 65litre planted tank) your articles are very helpful, and really reassuring!

We’ve got brown algae, which I’m guessing came about because we fed them brine shrimp – because we have only 7 fish, the lovely shop people recommended feeding them the packet over 2 days.

The rasboras loved them, but our betta would take one in his mouth, chew it for a bit, spit it out, catch and chew it again, spit it out, chew and spit it a third time, and leave it. It was ok when he was in the middle & top layer, as the rasboras would eat it, but all the ones on the bottom got chewed and left. We did a 50% water change and tried to vacuum the little corpses, but there were a lot left.

We’re not going to try more live food until we get our corys, in another week, but we have the little stringy brown algae you describe. I want to get a nerite snail, but I’m wondering if that will eat the algae from the plants? At the moment it’s only on the small leafed plants like water lobelia, and the spines of others, which would be v hard to clean, but as they’re still pretty new, I’m worried about uprooting them.

Should I get chemicals, or get a snail and wait for it to clear up by itself, as my tank is still new. I’m regularly testing with my chemistry kit, and it is a very hard water area, but all the fish and plants from the local shop are bred/grown in hard water.

Thanks very much for your site, it helped make me feel like we could be ok having a tank!

Hi Sara,

Welcome to the hobby! It sounds like you are setting up an amazing tank.

While I love the idea of “clean up crews” such as a nerite, for many things, they don’t work as well as they should. A single nerite isn’t going to clean up every last piece of brown algae in your average bloom. Plus, he might not want to eat the algae from your plants and go for the easy to reach stuff. I only recommend adding things to your tank that you would otherwise want to keep there, as once the algae is gone, you still have an extra critter to care for.

As for chemicals, I try to avoid adding them wherever necessary. Not only is it *another* cost, but they can really mess with your water quality and fish.

My personal opinion on brown algae is to check you water parameters with an aquarium test kit, make sure everything is normal, keep your tank super clean and only stress if it doesn’t go in a 3-6 weeks. Unless it completely covers your plants from head to toe, your plants should still be able to photosynthesize (take in light) they will just look a little ugly in the mean time.

Unfortunately, a lot of fishkeeping is all about waiting.

Just as a quick trip. I would hold off on the Cory’s until the tank has been up for at least 3 months. Most cat fish like Cory’s do not have scales which makes them very sensitive to changes in the water.
Also for feeding shrimp, I have a straw that I use to scoop just a small amount of shrimp with and feed them what they will eat. You could also try freeze dried shrimp. It has more nutrients than frozen, and it is easier to feed in smaller quantities.

Okay I’ve had 15 aquariums in my life but I recently got into planted tanks….of which I’ve become obsessed with. I see some brown spots on my crested Java fern and on a narrow leaf temple plant. Yes, I know these propogate that way by sprouting new leaf growth with a small root shoot out but I hope it’s just that and not BBA or brown algea. I just started dosing Excel yesterday which I had planned to do already because I’m not comfortable going high tech yet until I get my Fluval Flora 14.5 gallon kit. Thanks.

I have a tank that has 1 betta fish and (had) a nerite snail for 1.5 years now. My nerite snail just recently died 1 week ago by now and I never realized just how much that snail was helping to keep this stuff at bay – never really even noticed it before. But my tank is now starting to be overrun by the brown gunk!
definitely going to invest in another snail… miss that little guy and his hoards of poop :'(

Hi Kay,

It sounds like you accidentally solved your algae problem and you didn’t even know it! Sorry for your loss, I hope you can find another hungry snail to replace him soon!

Thanks for the great article!

I have an established tank that is almost 5 years old. It used to be beautiful. My plants were thriving. About a year ago, I had a BGA outbreak. Then came the BBA. Now, I’m dealing with brown diatoms. I can’t keep plants alive. They’re all getting choked out.

Any advice for how to battle BGA, BBA and brown diatoms at once? Should I focus on one thing first?


Hi Paul,

That sounds like quite the string of bad luck, when you test your water, does everything come back within the expected range? I only ask as outbreaks of various types are often linked to a nutrient imbalance.

I cant say I have had any experience battling that trio at once. If I was ever in the same situation, I would probably start with the BGA. Then diatoms before the BBA. However, removal won’t solve these issues if your water is “out”

What’s BGA and BBA . I also have brown algae and I’m constantly cleaning the plants. They just arent growing. I have well water and was wondering if health department could let me know exactly what’s in my water

Hi Kathy,

Blue-green algae (BGA) and Black Brush algae (BBA) are different types of algae. I am unsure as to the process of testing well water since it’s composition will vary from location to location. If it’s from a water supply, the supplier can provide you with the results of their testing. Typically for well water I imagine you would need to have it tested yourself.

Hi Paul, I have a 5.5 gallon tank with a male Betta. I’ve been battling brown algae and I’ve done all the correct cleaning tactics to rid it but it keeps coming back. Two things may be an issue, one is I’ve never actually tested the water and there may be an imbalance so I will have it tested and I will look into reverse osmosis water. The other thing you mentioned is water current, and because betta’s don’t like moving water, we intentionally impede the water movement so he can swim freely. What is the happy medium between enough movement and not too much? Appreciate your input.

Hi Joanne,

Not a problem, I’ve been called far worse 😉

I would start by testing your water quality. I personally recommend the API master test kit. It will have every test most fishkeepers, it’s very had to troubleshoot without one.

If your betta can happily swim, then the current is fine. If it looks like your betta is struggling, or is being blown around the tank, then it’s too much. It’s hard to be exact here, different betta have different tolerences. When in doubt, for a betta at least, it’s better to have too little than too much.

Hi I have had Bettas for a couple of years, and I use snails to keep there bowls clean. I am not sure what type of snail they are, but they stay small and do an excellent job. They were a type of hitchhiking snail that I got with some live plants.

Sorry, Ian I called you Paul in my previous question. Also want to let you know I read quite a few articles about brown algae and yours was by far the most helpful.

What is the ideal phosphate level if you want to strike a balance between brown and green spot algae? At present I have 1ppm phosphate on my 75G aquarium. As you said if there is a presence of phosphates it will encourage growth of brown algae. However, for green spot algae, it is the opposite. Not having much phosphate will encourage growth. What is the sweet spot?

The brown algae appeared first a few weeks back. I added phosguard filter media some time ago plus UV filter and CO2 and this algae appeared to be well-controlled now. However I started noticing the green spot algae (hard to spot though) on the aquarium glass and on some plant leaves.

Hi Christopher,

This is actually a good question, brown algae typically goes away on it’s own and should be the least of your concerns at this momeny. I suspect a lot of these nuisance algaes have appeared on account of the tank being overstocked and the nutrient balance being off. I would focus on the stocking issue first, then tackle the algaes. For example, in an overstocked tank plecos can produce enough waste that algae can flourish. The greenspot is more likely to require manual intervention but if you do not have the stocking levels right first, then it will likely return.


I think I am on track now when it comes to stocking. From, I am at 101% stocking level if I get rid of my 2 common plecos and replace it with 1 bristlenose pleco. I can move a couple of mollies to another aquarium so that would bring it below 100%.

I already scraped the green spot algae from the glass but removing the tiny spot from some leaves are challenging. I also have staghorn algae on some plants but I am dosing them carefully with Seachem Flourish Excel now.

Though I lost several fishes… I learned a lot from this experience… and I learned all of these from you.

Hi again Christopher,

That all sounds really positive on the stocking levels – bristle nosed pleco are really neat fish too, I don’t think you will regret swapping them out. I know the die off was hard to deal with, but your tank will be better off for it.

For the green spot algae on the leaves, assuming they are not the final ones on the plant, it’s often easier to just snip them off. It may make the plant look a little sparse for a month or so, but as your plant grows, you won’t notice it.

Glad I could help. I hope it sets your tank on the path to success!

Hello Ian,

Otocinclus do not appear in your list of freshwater algae eaters. I suggest that Otocinclus need to be added to this list. Otherwise, an excellent article.

Definitely. My otos sadly passed away and within 3 days theres was brown algae on the glass. Never had a problem with the brown algae until the otos died.

Hi Ian,

I’m a new tank owner with a dwarf gourmani and a guppy currently. I got these fish about a week or two ago but this hasn’t been my first tank. I just started to notice the brown algea on the walls and fake plants I have in my tank. Is it possible that I’m allotting too much light for the fish? Also, in the other comments you mentioned giving something for the brown algae to feed off of. I currently am only feeding my fish bloodworms so could that be a possible cause? How long should I wait before starting to worry? Also, should I try and clean it completely off or wait for the problem to resolve itself?

Thank you so much- Paige

Hi Paige,

Brown algae is common in a new tank (has it been cycled?) and generally goes away on it’s own. When it arises in my new tanks, I give it around 6 weeks before investigating further.

i have a 30 gal tank used to be salt for a puffer. it got diatoms. i could never get rid of them. i eventualy rehomed the puffer, gutted the tank scrubbed it. put in all new substrate and deco. i how have 1 beta and about 20 guppies in it. and somehow the diatoms are baclk with a vengence. its only this tank my 45 and 65 never have had any problem like this. im at a loss.

Hi Edmond,

Is this a new setup and has the tank properly cycled? In most cases the diatoms go away on their own.

no ive had the tank running as a guppy tank now for 6+ months.
ive cleaned it comes back. ive cleaned it off and done a 90% water change and it comes back.
im at a loss. ive had 2 filters on it no change.
im wanting to set up a sump for all my tanks but dont want to get the diatoms in the other tanks so ive been waiting.
could it be that the tank used to be salt and i somehow didnt clean it well enuff when i removed the sand?
this is the only tank ive ever had this problem with.

Hi Edmond,

That’s an interesting point on the sand. It is suspected that brown algae feeds off silica and many types of sand contain silica in the form of quartz. This *could* be a possibility, but only you would know for sure just how well you cleaned it.

do you know of a diatom eater? that would get along with 20 guppies and a betta?
i have a feeling im only gonna be rid of this if something eats it.

Hi Ian,

Almost all good information, but as a recovering marine biologist… Diatoms are algae, and brown, but they are not brown algae, and not animals. What you are describing may be called periphyton, which contains a lot of diatoms. They do need light, not necessarily bright light, but they are photosynthetic. None of that in any way takes away from anything else that you have said about the problem or how to deal with it.

Hi Dave,

Thanks so much for this extra reading, I really appreciate it. I think you may be on to something here. It is possible that this was given an incorrect name and it is now commonly repeated in the hobby. Unfortunately, if I was to use the term “periphyton” at my local fish club, they wouldn’t understand what I am saying. The phrase, diatoms and brown algae are both used interchangeably to describe this in fishkeeping.

The common names used in the hobby work for the people who use them. An academic audience is different. I didn’t remember (if I ever knew) the term ‘periphyton’ until I looked up the links about diatoms this morning.

That’s a good point. I was considering adding this clarification to the guide after your comment but after considering the target audience with your follow up comment (mostly newcommers to the hobby,) I think I may skip it. I do have to thank you for dropping your wisdom on me though, one of the things I love the most about this hobby is that even after 30 odd years, I am forever learning new things!

When you say “recovering marine biologist” are you still active in the role? I’m actually very curious as to what fish and critters a marine biologist would choose to stock, given your expertise in the area. Do you choose fish that are more difficult for someone without expertise to keep? Or do you prefer to keep maintenance as low as possible?

Time and space for fish resulted in the low maintenance route. I am learning from you here. Except for a particular detail concerning diatoms. The job market in marine biology involved french fries and mop buckets so I went in the opposite direction; space craft. They can be interesting, if a bit dry.

Hi Dave,

It sounds like a good career shift. I spoke to one marine biologist who worked at a public aquarium. His job was to cut up heads of lettuce for 9 hours a day for a hungry herd (not sure if that’s the right grouping) of dugongs. I honestly with the field was respected more.

And please reach out if you get stuck. I certainly don’t have all of the answers, but I do have some. However, given your keen eye for detail and strong analytics skills I think you will be fine here!

Time and space for fish resulted in the low maintenance route. I am learning from you here. Except for a particular detail concerning diatoms. The job market in marine biology involved french fries and mop buckets so I went in the opposite direction; space craft. They can be interesting, if a bit dry.

Interesting, you can edit or add to a reply.

I read a little more, and in defense of the misnomer ‘brown algae’ it looks like it is a variation on the general theme of Peryphitic biofilm, periphyton, epilithic biofilms, or whatever you call the scum that coats everything under water. Pretty much every surface has a biofilm, and an out of control brown one is full of benthic diatoms. So brown algae is as good a name as any. They might be interested to know that this particular brown algae scum is not the same kind of brown algae as kelp or sargassum.

Ha, Dave, I think you know more about my website than I do. I’m not very tech savvy and had no idea you could edit or add to replies!

Thank you so much for the clarification again. I will definitely include this tid-bit when I update the guide, I like the reference you made to an “out of control biofilm” – it describes it really nicely.

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