Why Does my Fish Tank Smell? The Ultimate Solutions

Having a fish tank is a common problem you might feel that your tank smells like a “mild earthy aroma” or “freshly tilled soil” which is actually not harmful to your fish.

It is normal to have a mild type of smell which is not noticeable until you are near your aquarium.

Any strong smell that is noticeable outside of the aquarium or in the room where the aquarium is settled, indicates something wrong with your fish tank.

In my experience, I can say the most common unnatural stinks are sulfur, ammonia, and musty whiffs which are removable.

In this article, we will go through identifying why a fish tank smells bad and how to fix it.

Why Does My Fish Tank Smell

No matter how much you care about your fish tank, a bad smell can happen to all aquarists. 

There are many reasons why a fish tank smells, and some of them are totally natural that are not harmful rather good for health to your fish.

Though a strong smell is unpleasant and embarrassing, it can also be risky, which can happen sick and make your fish die. 

Keep in mind that the longer you wait to repair, the more danger it will become.

Here are some reasons why your fish tank smell:

  • Dirty filter
  • Dead fish
  • Overfeeding
  • Dead plants
  • Fish poops
  • Fish waste
  • Ammonia
  • Fish mucus
  • Bogwood
  • Anaerobic activity

Dirty filter: In the aquarium, a filter task is to remove nasty things from the tank water. A filter collects anything that is unnecessary to your fish which makes fish tank garbage. Even afterwards, the garbage can become stinky itself.

If you notice the smell has come from the surface of the tank, check to see if it’s a filter. Filters that have smell might be full of dust or no longer able to work what they should.

Dead fish: Dead fish could be the cause of bad smell if they are left for a long time in the aquarium.

Though many fish float after they die but some of them get stuck into the filter. Even some of them get stuck into the rocks, driftwood, or plant leaves at the bottom of the tank.

Overfeeding: Uneaten food remains at the bottom of the tank, under the plant, gravel, or gets stuck into the filter, which helps to grow excess gas that creates mouldy smell in the tank. 

Overfeeding also increases the fish poop and makes them sick early. Besides this, you have to make sure you are giving the right type of food because the wrong food, fish will not like to eat, and the remaining food will pollute the tank.

Dead plants: though plants are useful to fish and they maintain a natural environment in an aquarium, they can be the cause of fish tank odour. 

Plants continuously grow and produce lots of leaves, and some of them can die in the aquarium, which could remain at the bottom of the tank.

The dead parts of the plant release gas into the aquarium and whenever the fish hang out in the filter area, the bad smell you can realize.

Fish poops: it is logical that having too many fish in an insufficient place that will create too much poop in your aquarium. Like other garbage fish poop also makes a tank smell bad. 

Though a fish tank filter can help to get rid of poop, But having too many fish, the filter may not be able to destroy enough poop from the tank water.

Fish waste: There is the most common problem in an aquarium that is ongoing fish waste which is another cause of “fish tank smell”.

The smell which comes from fish waste is normally slight, but the only extreme odour will come when you have so much fish waste.

Ammonia: Once you know how ammonia smell like is, the rest of the time you will identify the ammonia smell. The ammonia smell is like salts, pee-filled babies’ and nappies which is like ironic, is used to clean household products. 

Above the 0 PPM of the ammonia level is harmful to your fish because it is toxic and can make odour in the fish tank.

Fish mucus: The mucus protects fish from “invading pathogens” which is like a guard system in the fish body. The decent mucus is helpful to fish health, and it is essential to keeping fish well.

But the extreme level of mucus sometimes can make the bad smell around the aquarium, which is created from poor water quality.

Bogwood: Bogwood is a wood that is suitable for aquarium and is named “Bogwood” because it is easily dug up from the peat bogs.

The new wood sometimes releases tannin and changes the color of the water like tea, and it could be a cause of bad smell in the fish tank.

Anaerobic activity: Usually “Anaerobic” stay where either low level of oxygen has or there is no oxygen is available and they produce rotten egg smell in an aquarium.

The remedy of anaerobic bacteria is to clean the substrate and gravel regularly with a vacuum. The vacuum can help to keep the substrate, gravel, sand, and other ornaments germ-free so that anaerobic bacteria cannot be able to build up in the tank.

Why Does Fish Tank Smell like Rotten Eggs or Sulfur

Fish tank smell like rotten eggs or sulfur indicates that your tank has serious harmful bacteria problems that might occur for using of imbalance chemical or damaging filter or air pump in aquariums which is an unhealthy and stressful environment for your fish. 

To keep your fish tank from rotten egg or a sulfur smell, you should always keep the tank clean and all the maintenance to be working well.

Get a habit of removing uneaten food and other types of debris from the aquarium, which make the filter clog can give you rid of the sulfurous smell.

 Besides this, you can 10 to 20% of partial water changes to keep the tank water clean, which can also give you redemption of rotten egg smell.

Why does fish tank smell Like mold

As an aquarist, you may probably notice that your aquarium smell like mold But actually it wouldn’t mold but algae or fungus.

 Mold grows in an aquarium is rare to happen, but it is not impossible to grow there.

In the aquarium, mold may be created by the “blue-green algae” or “cyanobacteria” most often which is considered for the moldy smell.

It is said that blue-green algae are not actually algae, but bacteria that have various types of spices act in different traits.

If the moldy smell you think comes from blue-green algae, it will be associated with the tank you can see by visible on aquarium glass, rocks, driftwood even on fish.

 In some cases, these visible things would be brown algae ( diatoms ) which is odorless, but once it is out of control, the whole room would be the mold smelly.

How to Get Rid of Fish Tank Smell

To get rid of fish tank smell, make sure you have identified the source of reason why your tank is smelling (which are discussed above). 

Try to find are there any missing in the aquarium? If so, I think you know what you should do.

 But if you have any confusion to find the exact reason where odor comes from, follow the instructions to remove the bad smell from the aquarium.

  • Clean substrate using vacuum
  • Remove the dead leaves
  • Clean decorations
  • Control overfeeding
  • Do a regular water change
  • Clean all the other debris
  • Check the filter pads
  • Add carbon filter (If possible)
  • Control ammonia

In order to keep fish tank odour-free, you should maintain some basic daily, weekly and monthly maintenance which depends on your aquarium size, where it is placed  and some other things.

Each tank and fish behaviour is different from others, so the “maintenance schedule” should be also different from what someone follows.

There are some factors to determine what should be an aquarium maintenance you can follow:

  • Tank Placement
  • Tank size
  • Filtration system
  • Feeding habits
  • Size of fish 
  • Number of fish

Daily maintenance: Fish is like a sensitive animal in your house between other types of pets. so they need daily care. 

Though fish do not need the same demand for daily care but they need to look after daily basis. In the daily maintenance you should look after the following things:

  1. Feeding 
  2. Water temperature
  3. Equipment check
  4. Behaviour check
  5. Water check

Weekly maintenance: After daily maintenance, there is some extra care you need to do a weekly basis to keep your aquarium and aquarium fish well.

  1. Plants
  2. Algae
  3. Water changes
  4. Glass
  5. Substrate
  6. Driftwood

Lack of proper maintenance in an aquarium can make your fish tank smell bad. So it is important to do proper maintenance to keep fish tanks odour free.

Keep in mind that more fish in a small container will increase more debris that will be converted into the odour. Besides this, feeding is another major problem of creating odor. 

When you will feed your fish try to feed them as a small part. So That, fish can finish it under two minutes during the feeding time. As a result no extra food won’t remain in the bottom of the tank.

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