I have a tank with one fish, and a common algae eater pleco. The tank is clean, no gravel, no dead fish. The filter is clean and works properly, and we do water changes as need be, such as once a week. Why does my tank have such a fowl odor??
Could be uneaten fish food lodged under the top rim of the tank somewhere, or on the underside of the hood/light.
Other than that, a properly maintained tank and filter should not stink and would generally be a sign of poor water quality (not enough water being changed) or a filthy filter.
How much water do you change? How big is the tank?
Odor is typically a sign of poor water chemistry, meaning you aren't changing enough water or often enough or aren't gravel vacuuming enough.
I have a tank with one fish, and a common algae eater pleco. The tank is clean, no gravel, no dead fish. The filter is clean and works properly, and we do water changes as need be, such as once a week. Why does my tank have such a fowl odor??
Some smells are normal for a new tank. Mostly they are a kind of plastic rubbery smell kinda like the smell of water from a garden hose in summer.
Other smells are not normal. These Ted to smell like eggs etc.
If your water has an odour to it the fish tank can amplify them if you have an air pump making bubbles as it will allow the organics to evaporate at an increased rate. This is also normal.
And all of this can be remedied but you need to give info on it.
What size tank.
What occupancy of tank
Age of tank
How long tanks been running
What the smell resembles
And water quality tests results if available