I literally just brought one back to my local marine center after it dominated an entire 55g at less than 3" in length. Every single fish in the aquarium was larger, and by the morning all of them were at the surface looking up at the heaven's for help. Bare in mind that the fish was the size of a quarter just 2 weeks ago. I had watched it grow in the aquarium at the store, then decided to add it to this tank before transferring to a larger tank.
What I have learned about this fish is that it is unwilling to have any tank partners, small or large. I have other cichlids that are super aggressive and this one puts them all to shame. I actually signed on to the website after viewing for many years just because I wanted to get my 2 cents in on the Butterkoferi.
If you like having 1 fish to an aquarium that both intelligent and vicious, get one. If you want to have a nice setup with natural plants and other similar sized fish, just give up... when you remove the fish that's getting picked on the most, the Butterkoferi will just move on to the next one, and so on and so forth until it's just him remaining.