Fin rot is a common symptom of a fungal disease that can affect a variety of fish, from Betta fish to goldfish. It is often caused by a dirty tank, poor care, or exposure to other fish who have infectious diseases. Your infected fish may have fins that appear to be torn and ragged, as if they are rotting away. The fin rot may also cause your fish to become discolored and lethargic.[1] If fin rot is not treated properly, it can lead to permanent damage on your fish’s fins and be fatal for your fish. Fin rot is also highly contagious and should be contained as soon as possible so it does to affect the other fish in your tank. And also clean the fish accessories in the tank like decorations and such.