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Why Does My Fish Tank Smell

We all know fish is a sign of positivity and liveliness and having an aquarium in the house brings happiness and prosperity. But sometimes we observe some foul smell in the room. It feels bad when the smell comes from the fish tank, so Why Does My Fish Tank Smell?

There are multiple reasons behind the unpleasant smell which creates an unhealthy environment. Today through this article we will understand all causes with their solutions.


Top reasons why does my fish tank smell?

Initially, when a person installs a fish tank in his house, he’s not aware of the knowledge of taking care of and maintenance of their fish tank. Genuinely all the fish tanks are to be odor-free but when it starts smelling for some reason, then quick attention is indicated or needed.

Let’s find out which one of the following sources is the reason for your smelling fish tank. The top reasons include:

  • Dead fish
  • Overfeeding
  • Fish poops
  • Substrate
  • Rot plants
  • Aquarium filter


1. Dead fish

It’s tough to say but when your loved fish dies in the tank for some reason, it will create a whole fish tank odor very badly. This is the most common reason behind smell, and sometimes when a single inhabitant dies in the tank, it’s very hard to find due to its small size or the dead body of the fish hides between the decorative substrates or plants or lying at the corner of the tank.

When a fish dies the process of bacteria and fungi began in no time to decay the body of the fish and slowly ammonia and sulfurous compounds began makes a bad odor in the surroundings.

Dead fish

2. Overfeeding

In order to save our time or while hurrying we just put more food than necessary in the tank. As in result fish consume more than the dose of their one-time food which also may disturb their health performance. Later on, the rest food started settling down on the floor of the tank and slow bacterial growth started which later created chemical gases and start smelling.


3. Fish poop

Fish poop can also be the reason for the smell. The number of poops depends on the number of fish in the tank. The fish poops start smelling when it starts breaking down over the floor.


4. Substrate

The substrate is an essential component of the tank, with substrate we also add gravel, pebbles, sand, or soil for the plant roots, and a substrate also gives a natural and realistic look to the tank.

But over time it becomes a house of the bacteria that takes part in the nitrogen cycle. This provides a space for the dead plant matter and fish poops for decaying that later causes smell even after the removal of all the waste things.


5. Rotten plants

We all know that dead plants submerged in water given a decomposing smell. Although sometimes it becomes hard to notice whether the plant has died or not and we mostly identify it by its changing color which became brownish or blackish in color. Consistent lighting in the tank also leads to growing algae which later also starts to smell when starts rotting.


6. Aquarium filter

Aquarium filter is an equipment used for collecting the waste things from the tank. All the waste we discussed above can be automatically collected by an aquarium filter.

The aquarium filter has alone more sludge than the whole fish tank so it’s obvious to smell badly from the filter area. The smell sometimes can be very strong which creates a bad environment.


Methods of preventing bad smells caused by the above reasons

How to remove the bad smell caused by dead fish?

First, check the dead or decaying body of the dead fish and remove it manually from the tank. If a test kit is available to you then please check the quality of tank water that is already contaminated by the dead body, if necessary then please change it.

Cleaning tools

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How to remove the bad smell caused by overfeeding?

Please only give the proper amount of food. In the initial period, you can track and record what amount your fish are consuming and also can read the instruction on the label of the food. As for the knowledge, aquarium fish have a diet of as much as they can eat in the first 5 minutes (mostly depending on the species of fish).

The owner of the fish tank should take care of their fish with a different kind of food taste. But it is necessary to remove all the food waste over the granules or floor of the tank. We should always keep a clean environment inside the tank. And you can use an automatic feeder to control the time and food amount when feeding.


How to remove the bad smell caused by fish poop?

Make a weekly routine to clean the poops from the tank that will keep a clean environment. As it depends on the number of fish, fewer fish be easily monitored whether you can buy a larger tank or remove some of your fish but do not overstock fish in the tank.


How to remove the bad smell caused by substrate?

As soon we noticed some waste matter on the substrate part we should immediately clean the substrate by vacuuming the things with a gravel cleaner and should work on a weekly routine basis.

In the case of soil, after some months we need to change the soil as the plants have already taken out all the nutrients present in it. Over time the oxygen is not reaching the soil which leads to the growth of bacteria in it.

Gravel cleaner & Water changer

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How to remove the bad smell caused by rotting plants?

Plants should be in a proper condition where they get easy lightning and essential nutrients. If we find the brown leaf or any dying part of the plant then we should immediately remove the plant from the tank and dispose of or destroy it.

If you have a budget then you can add Malaysian trumpet snails to your tank. You will see the benefit that it feeds on the extra food left by the fish and also feed on the dead plants which somehow reduces most of the waste without applying any effort by your side.


How to remove the bad smell caused by the aquarium filter?

We should add a cleaning tank to our weekly routine. It is based on your filtration system that should be replaced with a new one or just clean and installed back.


Tips for getting rid of the smell forever

Similarly, the way we keep our house clean by regular maintenance, our fish tank should also need maintenance not as regular every day but we can make a routine on weekly basis.
  1. We should clean the glass from the outside and watch whether the lightning and filter systems are properly working or not.
  2. We can use carbon to remove the smell, as we know carbon has the ability to absorb the waste substances from the water. So, it will keep the waste particles away from the water and give your tank a crystal clear water appearance.
  3. Don’t forget to change the carbon on time.
  4. Change the water of the aquarium at least twice a month that will keep your fish collection healthy and live in a fresh environment.


Conclusion: Why Does My Fish Tank Smell?

Hope we have cleared all your queries through this article regarding “Why Does My Fish Tank Smell?” and providing you with which is best for your aquarium. If you have any unanswered questions or want suggestions for the products for your aquarium then please leave your message in the comment section.



1. How to get rid of the smell from your fish tank?
By taking regular maintenance and following all the preventive techniques mentioned above in this article.

2. Does bad smell bother fish in the fish tank?
Yes, they get stressed and that leads to changes in their behavior.

3. What is the sign of stress in fish caused by the bad smell?
We can read their behavioral changes like swimming at the surface area, pale color of their body, rapid breathing, and also the bloodshot fins appearance.

4. Does a bad smell also bother plants in the fish tank?
Yes, we can find some kind of stress in plants which leads to dead leaves, disease on the leaves, damage to the root part, and many more.

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