Why does my Fish Tank Smell?

Your fish tank may be smelly because the water is dirty. You need to understand that your fish eat where they excrete their waste, so the water in your fish tank is probably mixed with left-over food pieces and everything that is excreted by your fish. In addition, bacteria may be invading your fish tank and causing foul odor in there. If your fish tank is smelly, you should change the water more frequently so your fish can live there happily.