Originally Posted by Dead Sunlight
I see Dead Sunlight tail bite all the time:(
Really? This fish must be very neurotic or stressed to bite right in front of you. It may also be a sign of poor breeding--some theorize that tail biting is an inherited trait.
It looks to me that the fish is nibbling on his fins. I don't see any signs of infection. The notches you're seeing are the places where he's taken bites. Fin rot does not look like that--it's much more even and is discolored. There are ways to help stop your fish from doing this, but you have to figure out what the root of the problem is.
Some biters bite to relieve stress--I have had two of these in the past. One of them was a very high strung fish who did not like to have anything in his aquarium change, and he especially did not like total darkness. If I kept the room totally black, I would wake up to a totally nommed up tail. Once I started keeping a nightlight on, there was a lot of improvement. Another stress biter I had simply hated one particular piece of decor--it took up too much space in the tank or something. Once I removed it and added some leafy plants, he stopped biting.
Some biters bite to relieve boredom or out of hunger. I have one of these now, I skipped feeding for 3 days while I was on vacation and came home to a mangled tail, zzzz. Jerk. I usually keep him controlled by moving around his decor and giving him new things to look at outside his tank.
Some fish bite for reasons we just don't understand, and as I stated before, it has been theorized that biting is an inherited trait. It may help to review your care habits and his environment and try to figure out whether he is being exposed to stress or whether he's simply bored.