Originally Posted by fish monger
Well, his fins were smooth on the edges last night. Today, it looks as if at least 1/4 of an inch has been torn away from the "spines" of his fins. I've just recently heard of them nipping at their own fins. What causes that ?
This would happen if your betta has extremely long fins.
You can check out this great advice:
What I want to emphasize here is that you need to make sure that he is actually biting biting his own tail. Observe him for a while. It could easily be that he is getting his fins ripped on aquarium decorations. Do read the advice on the link I gave you, I think it's great. Good luck! :)