See thing is all could be well for a few weeks or months, until something pisses him of and he goes nuts and kill everything that moves.
I got two one is 6" and leaves 2" convicts alone while the other is maybe 4 inch but will kill anything when ever it feels like. For example he could not catch some feeder minnows so he decided to destroy the tail fins on 3 jewels cichlids. Or if the gold fish was to big to eat he'd still tear their fins apart and kill them.
Only way to make them some what peaceful is keep them well fed and NO live food. And make sure tank mates are bigger then it.
Also some fish are just more aware of what they are up against, some of my dumb cichlids will steal his food, while my pike stays the hell away from the wolf. Seems like the other predator understands what that monster is.