I'm new to this. I have blue tang, 3 damsels, clark's clown & 3 other little ones. These fish have been together for a while with someone that gave me the tank. When I put a new jawfish in, they bite at it and pull it by the tail. The next day it was fine. Today I put in a clarks clown and they were doing the same thing but a little worse. He finally is now hiding under a rock. Is this normal? Any input would be great.