What is it youre after? Do you want a fish that will kill others? Do you want a fish that will claim a large territory and try to attack you through the glass? It depends on the size of the tank theyre in and the aggression level of the individual fish. I have a 7 Red Devil in a 75 that has claimed half the room as his turf and will attack anything it can see with gills flared back hunched and snapping like a psycho maniac. He would probably calm down in a larger tank, maybe not, but I dont have one right now to put him in. I have another 9 RD/Midas in a 180 thats no more aggressive than a large Severum. So again I ask you what are you after. Both of these fish are beautiful, get very large and require a very large tank to do them justice. If you want one because you appreciate their beauty and behavior that one thing if you want the biggest bad fish on the block look elsewhere. I didn't mean to rant, but those kind of questions send up red flags.