they are great.. i love mine, but mine are the red ones.
the problem is, they like to have a spot that is all theirs, mine have killed angel fish, and a BIG BGK because they tried to hide in "their" spot..
i think the angel fish just didn't give a damn and swam where they wanted.. lol. but one by one they lost their fins and then died when they were in the 100 gallon tank with the snooks.
i've got them with bigger and tougher fish (cichla) now, i still worry a bit about my CK, but i don't have another tank that he can go in, and he seems to be holding his own (going on 6 months now).