I've come to the conclusion that Paarthurnax is a tailbiter!!!! Any ideas as to trying to get him to stop? I tried the clean ping pong ball on top and he's not interested. He does chase the laser light a tiny bit. I even bought shiney gems for his tang to put in after next water change, which is today. But, it just looks like I'm going to put him into the hospital tank. It got a lot worse when we were sleeping!!! Was he biting in the dark, when he should have been sleeping? Any ideas are welcome!!! Thanks!!!