I have a wild caught male in my 125, with a group of tropheus. He has never been aggressive towards the other fish in the tank. He used to be housed in a 75 with mostly the same fish along with some brichardi and was not a problem there. However, the guy that I got him from said that he had him in a 180 with 3 other petrochromis females and he killed all of them. In the setting he is in now, he is quite mellow and eats like a pig. He is about seven inches in length and is one of my favorite fish.