I ask this question because I recently had to donate my full grown Buttikoferi back to the store I purchased him from as a small fry about a year ago. This fish killed the longest tenured fish in the tank, which was the Red Tiger Oscar that you see in my avatar photo. He harrassed the other fish into submission and would charge at the glass whenever ANYONE came near it! At the fish store, he charges the glass and the owner says that he's a big attraction there and that the sale of his Buttikoferi fry is off the charts now. I don't know what species are compatible with this breed. What was the most belligerent YOU have ever had?