Stinky Fish Tanks
Why Does My Aquarium Smell, and How Can I Fix It?
(The First Tank Guide)
Most often, an odor from a fish tank is an indication that something is rotting in the tank. This could be:
- A dead fish (or other critter - snails and other invertebrates are often very smelly when dead) which has lain undiscovered in, under, or behind a decoration or has gotten caught in some part of the filter - or possibly that has just been floating around unnoticed and unremoved.
- Uneaten, excess food that was not promptly removed from the tank after the fish finished eating (typically about two minutes after the food was introduced to the tank).
- Dead plants or parts of plants that have not been promptly removed from the tank.
Insufficient water changes, insufficient filter maintenance, or other shortcomings in tank care can also be a source of odors.
Another possibility is that there is a reaction between some unnecessary chemicals you are using in the fish tank or between an unnecessary chemical and something in the water. I would recommend not using any chemicals in the tank other than a dechlorinator - and maybe a plant food if you are keeping live plants.
What to do:
If you have an odor coming from your fish tank, I would first check to make sure all your fish and other critters are accounted for and alive and healthy. Then check to see if there is uneaten food piling up in or behind decorations or in the filter, or if the filter cartridges otherwise need to be cleaned or replaced.
Also, reducing the number of unnecessary chemicals that are being used in the tank will probably help your overall tank maintenance as well as helping to prevent unnecessary and undesired odors.