Why Fish Tanks Smell: Eliminating Odors

Dirty aquarium filter system

Many people wonder, why does my fish tank stink? After a fish keeper starts up a new aquarium, there may be a slight fish tank smell. With that in mind, there should never be a foul or overall lousy smell near the tank. If the tank does not have an earthy aroma, then there is something wrong with the fish tank or inside the aquarium.

Why Does My Fish Tank Smell?

There are many reasons a fish keeper may start to smell something like sewage near the fish tank. What you're smelling is ammonia or fish waste. Gross! Your fish are living in a dangerous environment, and the tank may need a deep clean.

Top Reasons Why Your Tank May Smell Like Sewage

Care and maintenance are the two most important rules if you want to keep your fish healthy. There are many reasons your tank may smell, and this may be a reasonably easy fix. For example, you may have fish food on the tank's rim, which is easy to clean!

Air Quality and Humidity

Run a humidifier in the same room you have your tank in as moisture can build and cause the room to smell. That moisture may elevate the humidity enough to cause mold contamination in the room.

Dead Fish

Fish stuck behind plants and decorations may rot and decay. Dead fish are a terrible problem and smell awful.

Algae Growth on the Tank

You want to keep the algae content in the tank low. Remember that if your tank is in the sun, algae can multiply, so check the tank to see if algae are growing on it and grab an algae scraper pad.

Fish Food on the Rim

When fish food accumulates on the tank lid or rim, a foul smell can develop, which is very easy to wipe off. Use a paper towel and no chemicals.

Too much fish food in aquarium

Dirty Filter

Change your filter regularly. Filters may be the cause as they can smell terrible if you don't clean these with the water you removed from the tank during routine cleanings. The sludge or excess waste may be the issue, and you can tell the filter is not doing the job. Dirty filters smell like rotten eggs.

Check Out What's Happening Inside the Tank

What's going on inside the tank and in the water may also cause a tank to smell foul. For example, bacteria may become airborne with the evaporation of water.

  • The type of food may cause a foul smell, so check the pellets or flakes you feed your fish.
  • Overfeeding your fish gives bacteria room to breed and causes leftover food to rot at the bottom.
  • A substrate including gravel also smells like rotten eggs when the waste does not have oxygen.
  • Plant decay is common, and the leaves may start to discolor and turn yellow.
  • Fish poop produces waste products and becomes part of the indoor air environment.

Ways To Prevent a Smelly Fish Tank

The most important way to prevent a foul smell in your tank is to clean the filter. If your filter is clogged, it may need a quick rinse. You must wash the filter cartridge every week to prevent a smelly aquarium, so adding this task to your weekly tank cleaning process makes this easy. At this point, your fish may show signs of stress so observe the tank to see if they recover after you clean the filter.

Your Fish Are in Danger

The filter may be the source of the problem, so watch out for the rotting egg smell. When you smell any foul odor around the tank, it is time to investigate before your fish are sick. Tank maintenance is as essential as fish nutrition, so always look for the source of the problem right away. Sometimes the problem is easy to solve with a few short steps.

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Why Fish Tanks Smell: Eliminating Odors