i currently am keeping a true humu-humu trigger, along with a Niger trigger (and obviously other fish) i must say the humu-humu is pretty unpredictable in terms of compatibility, when i bought my black volitan lion,powder brown tang, and blue-spot puffer, my humu-humu didnt even bother them once. but i bought a rainbow wrasse and he just would not leave him alone and eventually killed him.ive noticed a trend though, my humu-humu will bump into a new fish and wait for a reaction, if the fish darts off and tries to get away, the humu will hunt it down and start beating it up. on the other hand, if the fish doest do anything or even goes after the humu, the humu accepts it and leaves the fish alone. My marron and yellow clownfish will actually steal krill right from the mouth of the humu...and gets away with it cleanly lol. Although he does intially want to attack any hand that comes into the tank, its simple and easy to "train" him to not attack your hand. i can now, after 4-5 days of repeated training, keep my hands in the tank for 30-45 minutes at a time without getting bit. on the other hand, my Niger trigger is nicknamed Dumbo...because he has nooo clue whats going on.. ever