I haven't had a problem with mine. I've got him in a 20 gal
with a pepermint shrimp.
HOWEVER, A jaw fish did die in the tank and the CBS decided that he belonged to him......... he carried him around for about 2 days before he finally finished him off. I didn't know wether or not to laugh or freak out because there was a slow rotting fish in my tank.
They are totally cool though. I would reccomend one to anybody. some peole say they aren't reef safe, but those people have never been pinched by one......... I have. Gettting bitten by a Maroon clown hurts a lot worse(and that didn't hurt at all really). So yeah they are territorial, but I don't really see them doing any real damage to anything.
Then again, you may get a super monster CBS on steroids that destroys your whole tank and kills you in you sleep.