How long have you had him? Mine was a model citizen for the first years and then turned into a messing piranha for the next six years. On the bright side, no ich for 10 years! He killed some seriously nice fish. A whole group of anthias, a mystery wrasse (also one tough fish btw), a solar wrasse, some clowns. Ugh. Finally gave him away to another reefer who had a massive tank. Last I heard, the guy trapped him and rehomed him to someone else. Apparently he was mean in the big tank too.You must just be unlucky? My Powder Blue Tang is just the nicest community tank member and is no problem at all. I guess you can never tell with fish, some individuals are OK and some aren't.