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Ever leaned in to admire your fish and recoiled like you just opened an old lunchbox?
If your tank is stinking up the room, don’t panic. The culprit is almost always one of seven usual suspects, and the fixes are surprisingly simple.
Table of Contents
1. The Smell You Should Never Ignore
If your aquarium smells like something died, chances are that something actually did.
A dead fish is the number one cause of foul tank odor, and the stink can spread through the room in no time. Even a single small fish decomposing out of sight can turn a fresh tank into a swampy nightmare.
The tricky part is that dead fish are not always easy to spot. Shy fish can wedge themselves into decorations or plants where you rarely see them, and jumpers can escape the tank entirely. If you have ever wondered whether your fish are auditioning for a magic act, it is because they are surprisingly skilled at disappearing.
That means your first move is always a roll call. Account for every fish in your aquarium and check behind rocks, under plants, and even around the stand. It is not glamorous detective work, but it often solves the mystery.
Where To Look For Missing Fish
- Behind decorations and plants
- Inside filter intake or tubing
- On the floor near the stand (for jumpers)
Once the culprit is removed, the smell usually fades quickly.
While losing a fish is never fun, the best way to minimize future heartbreak (and stink) is to focus on long-term care. Stable water quality, a balanced diet, and appropriate stocking go a long way toward making sure your fish live long, healthy lives.
Fast Fix: Do a headcount. If one is missing, search the tank and the surrounding area. Remove the body, and the smell should vanish.
2. Are You Overfeeding Without Realizing?
Most fish keepers have been guilty of this at some point. You love your pets, so you give them a little extra food.
The problem is that fish rarely eat everything offered, and uneaten food settles to the bottom. Once it starts to rot, your tank smells less like a peaceful aquarium and more like last week’s garbage bin.
The breakdown of leftover food does more than stink. As it decays, it releases gases and contributes to poor water quality, which stresses your fish. Over time, you might notice cloudier water, sluggish fish, and that telltale odor that tells visitors you have a problem.
The good news is that this issue is easy to fix. Feed your fish only as much as they can finish in about five minutes.
Start small, observe, and adjust. Different species and food types require varying amounts, so finding the right balance may require some experimentation.
Keeping food portions in check not only prevents bad smells but also improves the overall health of your aquarium. Fish that are not swimming in decomposing leftovers will thank you by being more active and colorful.
Simple Solution: Serve smaller portions and discard any uneaten food. Your fish do not need an all-you-can-eat buffet.
3. Poop Happens, And It Stinks
There is no way around it: more fish means more poop. And when waste builds up, your tank will start producing aromas better suited for a sewage plant.
Fish waste on its own is not a disaster. In a properly balanced tank, bacteria help break down the waste before it becomes a problem.
The issue arises when you overload your aquarium with too many fish or neglect maintenance. The result is an unmistakable odor that tells you your tank is working overtime.
New hobbyists are especially prone to overstocking, often because they underestimate the rate at which small fish grow or the amount of waste they produce. It feels fine at first, but a few months later, the tank becomes crowded, the filter struggles, and the water quality nosedives. That smell is your early warning siren.
Signs You Have Overloaded The Tank
- Water gets cloudy faster than usual
- Filter clogs more often
- Fish seem sluggish or stressed
- Odor lingers even after water changes
The fix is straightforward: stick to stocking guidelines, invest in a tank that matches your ambitions, and clean regularly. If you are already overstocked, you may need to upgrade or rehome some fish. A well-balanced tank smells fresh and earthy, not like it belongs in a landfill.
Key Reminder: Waste smells worse when it piles up. Keep stocking realistic and clean before the stink sets in.
4. Zombie Plants & Funky Algae
Dead or decaying plants can stink almost as much as dead fish. A once-vibrant leaf that turns slimy brown or black will release an unmistakable odor into your tank.
Add algae to the mix, and you have a recipe for a musty mess. Blue-green algae are particularly notorious for making a fish tank smell bad.
If your aquarium suddenly reminds you of a damp basement, it may be time to check your plants.
Rotting Plant Red Flags
- Slimy brown or black leaves
- Mushy texture that falls apart when touched
- Strong musty or moldy smell
The fix here is easy to see, but sometimes hard to maintain. Remove dead or dying plants quickly. Prune damaged leaves before they start to rot, and scrape away algae as soon as it appears.
Even better, recruit a cleanup crew. Snails, shrimp, or other algae-eaters can help keep things tidy between maintenance sessions.
Healthy plants not only improve water quality but also add natural beauty to your aquarium. If you want the good kind of earthy smell, focus on keeping them alive and thriving.
Quick Remedy: Prune and remove decaying plants if your fish tank smells bad. Add a cleanup crew if you want backup.
5. When The Filter Becomes The Funk
Your filter’s job is to collect the gunk in your tank, and it does that job very well. The problem comes when you forget to clean it. That pile of sludge and debris inside the filter does not just sit quietly; it ferments into a stinky stew.
If your tank smells worse right after a cleaning, your filter is a prime suspect. Fish keepers often focus on the glass and gravel but forget the filter housing, pads, and media. Out of sight should not mean out of mind.
Rinsing your filter media in tank water during a water change will remove most of the smell while protecting the beneficial bacteria that keep your aquarium stable. Skip the tap water, because chlorine kills the very microbes that are working for you.
A clean filter smells like nothing at all, which is precisely how you want it. Making filter maintenance part of your routine keeps odors down and water quality up.
Maintenance Move: Rinse filter media during water changes.
6. Rotten Eggs Rising From The Sand
Sometimes your tank stinks like sulfur. If that is the case, your substrate may be the guilty party.
Compacted sand or fine gravel can trap waste in oxygen-free pockets. When bacteria in these zones break down material, they release hydrogen sulfide gas. That “rotten egg” smell is unmistakable.
The gases rise through the substrate and into the water, eventually hitting your nose. It can be alarming if you have never encountered it before, but it is a common issue in tanks with poorly maintained sand.
How To Stir Substrate Safely
- Use a long stick or aquarium-safe tool
- Stir gently once a week
- Watch for bubbles rising from the sand
- Follow with a partial water change if needed
The fix is both preventive and ongoing. Regularly stir your sand or vacuum gravel deeply enough to prevent gas pockets from forming. Do not go overboard, though, since too much disruption can harm delicate plants or fish. Balance is key.
If you are planning a new tank, do your homework on substrate care before making a commitment. A beautiful sandy floor should be an asset, not a stink bomb.
Preventive Step: Stir the sand gently and vacuum the gravel deeply to prevent gas buildup before it becomes unpleasant.
7. Even Your Water Conditioner Could Be Guilty
Sometimes the source of the smell is hiding in plain sight. Certain water conditioners, like Seachem Prime, have a natural sulfur odor. Open the bottle and you will think someone cracked an egg under your nose.
The smell usually fades once the conditioner is diluted in your tank. However, if you add too much or have particularly sensitive nostrils, you might still notice it. Fortunately, this problem is temporary and far less worrisome than a rotting fish or compacted substrate.
If the smell bothers you, the solution is simple: choose a low-odor conditioner or use the recommended smaller doses. Do not be tempted to glug in extra, because more is not better in this case.
This is one problem where the stink is annoying but not dangerous. Still, if your tank reeks like eggs every time you change the water, it may be time to shop for a different product.
Easy Fix: Switch to a low-odor conditioner or double-check your dosage if your fish tank smells bad.
Clear The Tank: Three Steps To Freshness
Now that you know the causes, it is time to make your tank smell like it should. The three steps below will clear the air and keep it fresh.
Important: Make sure you have identified the cause of your bad smell from the list above. If you do not remove the cause, the following methods will not fix the lingering odor.
- Deep Clean: Wipe down glass, vacuum substrate, prune plants, and rinse your filter media.
- Daily Water Changes: For a few days, swap out 10 to 15 percent of the water. This dilutes the odor while improving quality.
- Carbon Filter Boost: Activated carbon in your filter absorbs odors and clears water. Just remember to replace it monthly.
Follow these steps and your tank will go back to smelling like fresh soil or a light ocean breeze. Your fish, and your guests, will thank you.
Frequently Asked Questions
Aquarium odor is one of the most common complaints new and experienced fish keepers face. The good news is that most smells have straightforward causes and solutions. Below are the questions people ask most often when their fish tank smells bad.
Don’t see your question? Ask us in the comments!
Why Does My Fish Tank Smell?
Usually, it comes down to decomposing food, a dead fish, fish waste, rotting plants, or a dirty filter. Sometimes the culprit is as simple as a strong-smelling water conditioner.
Do Different Fish Tanks Smell Different?
Yes. Freshwater tanks usually have a mild earthy scent, like damp soil after rain. Saltwater tanks tend to carry a faint ocean smell, similar to standing near the beach. Both are natural and pleasant in small doses.
If either smell becomes strong, sour, or foul, that is when you know something is off balance.
What Kind Of Water Should I Use For My Fish Tank To Avoid Smells?
Use treated tap water or distilled water. Tap is fine in most cases, as long as you dechlorinate it. Untreated water can destabilize your tank and create conditions that smell.
Can Bottled Water For Aquariums Prevent Fish Tank Smells?
Bottled water is unnecessary for most people. Unless you have highly unusual tap water, regular dechlorinated tap water works just as well. The extra expense rarely makes a difference.
What Is The Best Way To Get Rid Of Fish Tank Smells?
Consistency wins. Clean your tank regularly, change the water weekly, and ensure your filtration system is running correctly. Add carbon to your filter if you need a fast odor absorber.
Why Does My Fish Tank Stink Even After I Clean It?
If odors remain, check the filter and test your water. High ammonia or nitrite levels can cause lingering smells. Sometimes the cause is invisible to the eye but noticeable to the nose.
How Can I Prevent Fish Tank Smells In The First Place?
Do not overfeed, overstock, or skip maintenance. Staying ahead of waste and debris is the surest way to keep your aquarium fresh.
How Often Should I Clean My Tank To Keep It From Smelling?
A partial water change every week is a good target, with a deep clean once a month. Large tanks with few fish may need less, while small or heavily stocked tanks may need more.
What Are The Signs That My Tank Is Starting To Smell?
You should not be able to smell your aquarium from across the room. If you catch a whiff as you walk by, something is starting to go wrong. Trust your nose and investigate quickly.
Can A Smelly Fish Tank Make My Fish Sick?
Yes, a bad smell usually signals poor water quality, which can stress or even kill your fish if ignored. High ammonia, nitrites, or rotting waste all create toxic conditions.
While the odor itself does not harm your fish, the underlying cause definitely can. If your tank stinks, treat it like a red flag and act fast.
Keep Your Tank Fresh (And Even Better Looking)
Now that you know how to banish the stink, why not make your aquarium shine? Learn the 7 easy hacks for a crystal clear fish tank, discover the best aquarium plants for beginner fish keepers, and save time (and prevent future odors) with these automatic fish feeding hacks.
OMG. It was my pleco who had died. I had not seen him for a week which isn’t unusual. He is super shy. When I cleaned my tank looking for the smell, I found his rotting body. It was disgusting. I removed the body and added some carbon as per your suggestion. The smell was gone in under an hour. Thank you.
Hi Steve,
Oh no, that sounds like an awful surprise. I’m sorry for your loss. I’m glad you were able to remove the stink though.
I wouldnt use certain ornaments as I once found the skeleton of my plec trapped inside starved to death!!
My aquarium smells like rotten and the water is very cloudy, but I only have one fish and he’s perfectly ok. I already changed the water once, but it didn’t solve the problem. Any ideas?
Hi Nancy,
Are you regularly cleaning and maintaining your aquarium? Start by testing your water with an aquarium test kit, just to make sure nothing funny is going on. After that, regularly maintaining your tank is vital. For instance poop and uneaten food will fall to the bottom of your aquarium and gunk it up, requiring you to clean it with a gravel vac. As for water changes, you should be doing them regularly, not just when your fish tank begins to stink.
What’s regularly? Once a week? Every two weeks? We have the same problem.
Hi Veronica
It all depends on the size of your tank, the type of fish, filter system etc. Using an aquarium test kit to keep an eye on the water quality will give you a better understanding of what is happening in your tank in regards to water quality and how often you should be changing it. Water changes are typically performed every one or two weeks, during this time most hobbyists clean their tank too.
I changed my filter today and part of my water, but used a water conditioner for the rest. I also changed from sand to gravel, due to a problem with algae growing in the sand. Since doing this, the room the tank is in smells like a permanent marker exploded. What could be the cause of this? Are my fish going to be ok?
Hi Carson,
It’s possible that when you changed the sand, it released pockets of nitrogen gas that were trapped inside, which could be responsible for this foul smell. If this is the case, air your room out – open a window and get a fan in there. If the smell doesn’t come back, then there shouldn’t be anything to worry about.
I found this cool idea how to make a aquarium out of a ice tea jug with the spout to remove water. I have 1 beta and 2 miniature African frogs I know I put in one to many first the tank was cloudy went to petsmart and they told me to get a Moss ball put it in the tank and it cleared up but the next day it smelled like something was died in the 2 gallon tank. I have no filter or air pump. I have to keep a lid on the container because I have a cat and if he had his way he would be eating my beta. I have fine sand at the bottom and small rocks on top of that. I want to remove the sand and just keep white rocks. First should I get a air pump? and can I remove my plants out and all the fish into another container with the old water to remove the sand I don’t want it in there and I have 2 live plants. We have no room for a bigger aquarium and this one seemed to fit perfect on the end table. One problem the cat I have to lock him up in the bedroom while doing anything with the tank because he is wanting to get to the fish. The lip we have put lots of holes in it so all I want to do is start all over can I do that. I put out 2 gallons of water in a bucket yesterday with the lid on it because my plans where to take everything out of the jug remove the sand and put in the new rocks keeping the fish in the old water until I get the tank set up. I don’t have room for anything any bigger. this tank I just set up last Sunday. Gotta get rid of that smell.
Hi Maureen,
I’d say you are overstocked for a 2 gallon tank. It’s going to be hard work to maintain a tank this size – small aquariums require much more work than larger ones. Constant water testing and water changes will be key. If you are serious about this fish keeping thing then it will be easier to just get a larger tank.
It also sounds like you have not cycled your aquarium, an essential first step of fish keeping. White cloudy water is common on new tanks and generally clears up by itself – the marimo moss ball was unlikely to be the fix. I’d also suggest using an aquarium test kit, so that you can see what is happening in your water, it might give you clues as to why it smells.
Regarding your air pump question, if it’s for an air stone, betta prefer calm water.
I just started a 39gal tall cichlid tank. I have 5. I was wondering what the clear junk that comes out of nowhere is exactly. I do a partial water change almost daily because it’s bare bottom. I have a good canister filter, but the poop just sits at the bottom. I’m forever scooping it up. Ugh! But, that clear gunk is driving me even more nuts. Help!
Thanks
Hi Sheryl,
Could it be a biofilm that is feeding off nutrients in your tank?
I just set up a new 75 gallon tank. I only have 5 koi fish in it that are about 5 inches in size each. I feed them once a day. I have a sun sun 304b canister filter with carbon, ceramics, and bio balls. The tank smells kinda like broccoli. Its starting to smell up my living room. Ive done water changes and vaccuumed the gravel and it still smells. Any suggestions? I am going to try cleaning the intake and output hoses to see if that helps.
Hi Steven,
Firstly, It’s also possible that something in your new setup is giving off a funny smell which may disappear in time – cleaning pipes and equipment with vinegar before rinsing with freshwater may help.
However, I am concerned about the number of Koi you have in your tank…
That sounds like too many koi for a 75 gallon tank, especially for that size. It’s generally recommended that you only stock 1 inch of koi per 10 gallons of water while they are growing – so if a single koi is 5 inches long, you would need a 50 gallon tank for that one fish.
It’s possible that overstocking the tank is causing waste to quickly accumulate, causing the stench.
Ian I really need your advice. My son has a 55 gallon tank that had a massive algae bloom. We had been treating it with Prime but was told to use Algaefix to control the algae. It worked!!! However we have still been treating it and I fear that maybe we don’t need to use the Prime anymore. The filters are being changed when the indicator says to(about a week). He did have two fish die unrelated to this. His plaeco ate them. We are now left with a musty mildew smell and I’m afraid we are all gonna get sick. Last week we changed out half of the water. One side of the tank is in front of a window but he has a black out sticker on the back and we cover the side that’s infront of the window. How do I get this smell out? Please help!!!
Hi Myria,
Seachem prime, among other things, dechlorinates your tapwater. It will have no impact on algae. If you are adding in tapwater for your water change then you absolutely need to use prime – it will kill your fish otherwise.
What does your aquarium test kit say? This should clue you in as to what is happening in your aquarium.
If the algae bloom was white and turned your aquarium cloudy then it’s a natural part of the cycling process. If you have never cycled your tank then that is more than likely the reason why your fish have died. If you don’t know what I am talking about here, please read my beginners guide to the aquarium cycle. It is perhaps the most important part of keeping fish.
As for changing your filter pads once a week, that’s overkill and is possibly partly responsible for your tank problems. Grab a filter that doesn’t force you to use those nasty “disposable” cartridges, it wills ave you a fortune in the long run.
Even if fish die, it shouldn’t take much effort to remove the bad smell left behind.
Water clear no food debri any where fish healthy But still has slight pond smell, filter clean fish tank clean just a faint smell reminds me of a pond. ???? Otherwise everything excellent…..
Thank you…..
Hi Dale,
There isn’t really enough information to go off here. Can you smell it when you stick your head over your tank or from the other side of your room? If it’s the first one, it shouldn’t be an issue. Also, have you tested your water parameters? Is it a soiled tank? How often do you clean your tank Do you have too many fish? Etc. These things are easy to diagnose in person, but online it can be darn near impossible.
Hi Ian,
Thank you for sharing all this information. I’m looking for some advice.
I came back home today to see that my blood parrots have developed some white fluffy hairy (not cottony) stuff on their fins. I have a balashark and a sailfin pleco too in the same tank and they don’t seem affected at the moment.
I dont know what the issue is, although i noticed a piece of driftwood had quite a lot of white cottony fungus on it. Its been in the tank for 6months now but I’ve taken that piece out. I’ve put the other piece of drift wood and lavarocks back in.
The water also smelled musty and moldy. I’ve done a 50% water change and bumped up the temp to 30. I also dosed the tank with seachem paraguard. Im not sure what else i must do.
Please advice. Is this a fungal infection or is this something else? How to I save my fish?
Hi Kmenon
Unfortunately, without seeing your fish with good quality photos, diseases and infections are almost impossible to identify with just a description.
I’d suggest posting this to an online aquarium forum. Simply sign up and post a pic with your tank parameters, and others will help you diagnose what is going on with your fish. I sometimes do this myself when I want a second opinion!
Hi Ian!
I just got my betta fish two days ago. Today, the water became very cloudy and began smelling bad. I definitely over-fed the fish the first time because some food fell to the bottom of the tank. However, I read that the cloudy water could be due to microorganisms establishing themselves in the tank since it has just been set up. Today I did a 30% water change and filtered some of the gravel to get ride of any excess food sitting in it. The water is still cloudy, but I’m not too worried about it because I think it is just the tank cycling. However, the smell has not gone away so I’m considering changing the filter and putting activated carbon in the filter as well–is this the right next step?
Hi Grace,
It’s generally recommended that you cycle your tank before adding fish. Cycling is with a fish in the tank is a rough process and can cause fish to become sick or even die.
If I had to guess, did you buy your fish and setup from a big name petstore? Unfortunately, these places often skip telling you all the essential information. It’s not the employees fault, it’s just the training materials provided by management are not satisfactory.
I suggest reading up on fish-in cycling to give you a better idea of how beneficial bacteria establish themselves in your filter. You should NOT change your filter since this is where the bacteria live. Instead, rinse it in freshwater. Those disposable filter cartridges are terrible for the hobby since they actually encourage this to happen. Activated carbon is very effective at removing bad smells but it will not prevent the cause. It will also need to be regularly replaced as it can only absorb so much before becoming “full”
Have you tested your water with an aquarium test kit? This can provide clues as to why your tank stinks. You should already be doing this daily while cycling anyway!
My aquarium has been properly cleaned out as my shubunkin died of ich ???? and I used boiling hot water to clean everything and to kill the ich. After I cleaned everything and cleaned my tank I put everything back in and fresh water with conditioner, I left my filter running as might be getting another fish Saturday (black moor) but a strange smell is coming from my aquarium and idk what it is…. Please help
Hi Becky,
Have you tested your aquarium with a test kit? What does it read for ammonia, nitrates and nitrites? If you cleaned everything, then you’ll need to cycle your tank all over again here is a guide on how to cycle your tank. If you don’t cycle your tank, your next fish could get sick too.
I was given a 30 gallon aquarium. The water is very cloudy and smelly. I’m ready to clean the tan the tank again plus throw away the plants that were in there because they’re almost black and my tank is smelly. MY question is can I put real small seashells and mardi gra beads in bottom of tank for more color?
Hi Ellen,
Real seashells are going to rot in freshwater and make a bad smell. You would have to really clean them thoroughly first. I would suggest sticking to aquariums safe pebbles – these come in a wide range of colors.
I have a 10 gallon tank with 6 small (about 3 months old) guppies and 2 small…”moss” balls. I believe the tank is fully cycled, the ammonia/nitrite levels always test at zero with my API kit. The tank has been up and running since around 10/1/18, so about 4.5 months at this point. I used Seachem Stability and Prime in the beginning while cycling.
The issue I have is the tank has a slight musty, almost mildew type smell. I really only notice it when I open the lid but it just seems really weird. I also have a 28 gallon bow front tank and that tank has no odor at all, which makes the odor in the 10 gal seem more odd. The water is nice and clear, I haven’t seen any algae in the tank, the fish are acting happy, so it seems like almost everything is fine… it’s just this weird musty smell. I’ve done partial water changes (up to 30%) and it doesn’t change the odor at all. I’ve also washed the lid and left it outside to dry in the sun just in case the smell was coming from the lid. That didn’t help either. It’s getting frustrating trying to figure out where this smell could be coming from since everything looks clean.
I only turn the light on for about 6 hrs a day and haven’t seen much, if any, leftover food in the tank. I only feed them a tiny bit of food once a day and probably miss a day here and there. But the fish don’t seem to mind. They don’t even seem to mind the smell so maybe I shouldn’t worry about it, but it just smells gross to me. I was hoping someone might have a suggestion about what could cause a smell like this and what I might be able to try to remove the smell.
Thanks for any help/suggestions!
Hi Kristen,
If you look at your filter is it overly gunky? Or maybe your gravel needs to be vacuumed. Over time grime and gunk can build up here and can give off a smell.
In my case there was never any smell in my 100 gal tank, nor from my Fluval C4 filter when I did maintenance. Recently I changed to the larger FX6 filter to facility planned overcrowding. When I introduced the new filter I kept the C4 running as well for a couple of weeks to give the new filter time to get established. I then removed the old filter and left it unattended for about 4 or 5 days.
When I got around to opening it there was an overpowering sewer stink which despite spending a couple of hours of cleaning and allowing everything to dry in the sun is not as bad as it was but is still there. That filter had received new media only 3 weeks before the new filter was installed.
I can only assume that leaving that filter sit for nearly a week without flow of water and oxygen caused bacteria, good or bad, to die.
Hi Dave,
Your thoughts are entirely correct, the beneficial bacteria and any other gunk that has been trapped inside the filter has died and begun to decompose. I would imagine it was quite a stink. A vinegar soak works wonders for removing bad smells. However, if you have no plans for using the old filter then it will likely lessen over time.
I have a 63 litre tank with 3 mollies 1 yuppie 2 Cory’s ,it has started to smell ,I have tested it for everything and was all clear the only thing I have noticed that the sinking pellets take ages to be eaten sometimes never could that be the problem
Hi Gary,
Anything that decomposes can give off a stink. If you are not removing uneaten fish food, then it could be responsible for the smell.
I only noticed a smell in my tank since I put i a shbunkin fish. My question is: Do they smell worse than other goldfish?. I’ve had my tank over 2 years it never smelled bad until I put the Shbunkin in…
Hi Pat,
shbunkin shouldn’t give off a bad smell at all. Your first step should be testing water quality for ammonia, nitrites and nitrates, to make sure everything is okay there. Otherwise it’s likely one of the causes on this list.
Thanks for another useful post Ian.
Foul or odd smells are definitely a sign that something is wrong and can be the initial indicator of a problem. We have a 5 gallon nano that houses a Betta that was emitting a very musty odor, and even though the issue wasn’t clear at first glance, I found a dark corner that was a breeding ground for BGA. A BGA outbreak can foul up half of your house if your not on top of it, and if left unattended, will ruin a scape.
You can usually trust your nose to find something that is not quite right and rectify the problem before it gets out of hand.
Hi Again Ben,
That’s very interesting that you say that. I’m curious about your BGA outbreak. I’ve come across two different types, one had a foul, rotting swamp-like odor, the other just smelt like a normal fish tank, kind of earthy (I had no idea describing smells was so hard) In both instances, I was able to get rid of it with green slime remover.
I have had other readers state that either their BBA smells funny or it doesn’t smell bad at all. I guess there are multiple strains?
Out of curiousity, how did you get rid of yours?
I have a very bad smell coming from the fish tank. I set the tank up according to directions. I used bottled regular water. Water and setup were done 4 days before fish introduced. Bought fish at a pet store, Put fish in tank after acclimating them to tank. The next day I noticed an odor from the tank. I did some research and did the following—day 3 of fish intro, I started feeding only once a day, turned off the light at night, purchased a siphon took about ¾ of water out siphoned some junk out of the bottom and put in fresh water, rinsed filter, put in a bubble stone. About 3 days later smell back. I took a water test to a pet store. They said the water was prefect. They did not know what the problem was, they suggested I siphon more water and clean again. I siphoned more water off and three days later put in a new filter. The next day 1 molly died, I took him out and the smell was back bad. The other fish look as if they are not going to last long. The tetra are not eating and the pleco are always digging in the rocks. The smell is really bad, water is a bit cloudy but not bad. It is smelling up the whole room and hallway. Please help I think I have covered just about . that was covered that may make it smell. Help I cannot tolerate this smell.
I have a 5 gallon tank, came as a kit, with filter, water conditioner, I purchased heater, marbles and rocks, bubble stone, plastic plants, 1 molly, 1 barb, 2 pleco, 2 tetra
Hi Alana,
Firstly, your tank is too small for that many and type of fish. 5 gallons is suitable for a single betta only. You are going to kill a lot more fish if you don’t read up on what fish are appropriate for your sized tank.
Next, did you cycle your fish tank before adding fish? 4 days wouldn’t have been long enough to do that.
Finally, you should buy an aquarium test kit – it allows you to test your water at home and quickly identify these problems yourself. I recommend the API master test kit. It’s almost impossible to keep healthy fish without one.
A dirty petroleum odor came from my bonsai wood decoration, with java moss attached. To weigh it down I drilled some holes and with a hot glue gun, glued steel, not lead, fishing weights to the base. This was where the smell came from. I removed the weights and glue and am thinking of putting bamboo skewers in the base to stick it in the substrate instead of using glue and steel. Could it be the microbes that grow in the nooks by the steel weights smell like dirty petroleum? Or maybe it is what is in that hot glue gun glue? Ever heard of this smell? Thanks.
Hi Dan,
No, I have never heard of hot glue or steel being the source of bad smells, but there are some many different brands of hot glue that it may be possible one is stinkier? If it was a petroleum like smell, I’d definitely be leaning towards something man made being the cause though, so I suspect you may be right in your analysis.
Although steel should certainly be avoided for use in a tank given that it can rust and leach other nasty stuff into the tank.
I must commend you for narrowing down that as the cause, that would have been tricky to find!
I have a 10 gallon saltwater tank with two clown fish. I had the tank cycling for almost a month and a half with bacteria from another fish tank. Not awhile after I got the clowns I noticed almost white bubbly patches that look like maybe some type of mold or something. When I did a water change I got most of it out and thats when I noticed the smell. The tank doesn’t smell in general, only when I got whatever it is out. The water is also crystal clear. Any ideas on what this could be? Thanks
Hi Christina,
Does it match anything here:
https://www.reefcleaners.org/nuisance-algae-id-guide
How do you fix your fish tank if poop is in there without toching the poop
Hi Carolyn,
Are you talking about the poop that falls to the bottom of the tank and sits on the gravel? A gravel vacuum will help you with that.
Thank you so much for this information. I recently switched to a fine sand (My Mississippi Map Turtle loves it) substrate and I noticed a HUGE change in the smell. Turtles in general are dirty and need a lot of upkeep to keep things looking and smelling nice but I was super confused and concerned with the sudden and drastic change in the smell. I didn’t notice the smell until I went to clean the tank and lordy… was it bad! I’m guessing it became impacted and nasty gas was created so I will have to make a few changes. Thank you again for the awesome information!!
Hi Brittany,
Yep, I remember the first time I smelled that gas rising from a sandbed – it’s like a super charged fart wafting up into your nostrils… Horrible. I’m sorry you had to personally go through that experience.
I recently bought a used 75 gallon tank to use for my bearded dragon. I will remove the filter and cover the drill holes. I notice the empty tank smells a little like ocean. Can you recommend a cleaner for an empty tank and will not harm a bearded dragon?
The tank was really a good buy.
Hi Lois,
Generously wiping down with vinegar should remove most of the scent.
Hello!! I am here at 3:15am… Googling “egg smell in fish tank” has brought me here and I want to say Thank You!!! I had guppies that kept breeding for about 2 years and sadly after a water change from my boyfriend, they all died except my algae eater.. I cleaned my tank, waited a good few weeks took my 4 yo to the pet store and bought a pretty Oscar he named Cookie. He decided to dump all the food in the water along with pH and clarifier. I quickly took the fish out and cleaned the tank. 3 days later it smelt like someone died and my tank was very cloudy.. I noticed a white build up on the bottom of the tank so I went and bought a gravel cleaner, new filters and ammonia remover. I cleaned gravel and did a 50% water change now the water is clear but the smell still lingers. I will keep cleaning rocks and continue with 15% water changes thank you for providing so much information!!
Hi Jeanine,
A gravel filter is an absolute must when it comes to keeping an aquarium maintained. Cookie is a lovely name for an Oscar. Please note that oscars are messy eaters and you will likely need a weekly water change to keep on top of things – as always, act according to your test kit.
Hi
I’ve noticed a bad eggy smell from my 37 gallon. It’s not strong enough to smell in from across the room but if my head is like a foot from the hood there is a horrible smell. I have a AA green killing machine Uv sterilizer and there is no algae or cloudy water anymore.The filter is clean. I just changed the cartridge yesterday and washed everything. I did a 15% water change plus vacuuming all the gravel. No overstocking either. My new 10 gallon with no fish smells so good compared to the 37 gallon. Do you know any causes for the smell.
Hi Tom,
Does wiping down all the surfaces and stirring the gravel get rid of it?
P.S.
Also I have 1 golden nugget pleco and 5 otos they eat all the poop
They do NOT eat poop
So I have two beta fish in a 5 gallon and today it’s started reeking and my entire room began to smell like maybe rotten eggs and I’ve just cleaned the tank and I don’t know what to do to fix it or why it’s happening please help me
Hi Camilla,
Read number 6 – rotton egg smell is often caused by the substrate. If you stir it, does the smell get worse?
Hello, I am new to this fishy business . My toddler convinced me to buy a 5gl tank and 8 little fishies with a. I let mouse on their tails. By reading the comments I think I had too many. I was told to change the filter ever. 4 to 6 weeks. I haven’t even been 4 weeks and the water got cloudy,I noticed on Mother’s Day and the next day I decided to changed the water and the filter. All fishies are dead, I get so bad. I rinsed the fish tank, the stent h is not going away, I did hit water and I even used detergent. Nothing is eliminating the foul odor, it is also on the decorations and I don’t want to buy more. I did got rig of the gravel and ordered a. New bag, I also have new filters for a whole year in hand, I ordered a gravel vacuum and I plan on only buying 2 fishies next time. But I need to eliminate the odor from the decor and the fish tank. Help?
I’m so sorry that happened. The cloudy water and odor came from extra waste and a new tank that had not been cycled yet. The water change and full filter swap removed the helpful bacteria, which likely caused the crash.
Skip detergent in aquariums; residue can be harmful. To remove the smell, use unscented bleach at 1 part bleach to 20 parts water. Soak the empty tank, filter housing, and hard decor for 10 to 15 minutes, then rinse very well. Fill with tap water plus a heavy dose of dechlorinator, let sit 15 minutes, then drain and air-dry completely. For a final pass, wipe with white vinegar and rinse. Replace any porous items that still smell.
Start fresh and fishless cycle the 5-gallon. Run the filter and heater, add bottled bacteria, and feed the bacteria with a tiny pinch of fish food every day or two. When tests show 0 ammonia and 0 nitrite for a week, add life slowly. For a simple, happy stocking in a 5-gallon, go with one betta, or a small shrimp colony, and a nerite snail. Continue feeding the tiny amount, adjust the dosage to 30 to 40 percent weekly, and rinse the filter media in tank water, not under the tap.