I have had 3 triggers in the same tank before. First bought the Humu Humu (4"), then introduced a Niger (3"). Humu went after the niger, but nothing too bad. I then bought a larger clown trigger (5"). Dominated the Humu, but never actually bit him. They were all doing fine in the 90 gallon. Did a conversion on my 230, moved them in there. Bought a 6" emperor angel. Within 10 minutes, the clown trigger had killed the emperor. Didn't leave him alone at all for those 10 minutes - back and forth across the tank. I was prepping a tank up to move the clown into, but it was too late. I thought since the triggers basically left one another alone, I didn't have to worry about introducing an angel at all. Lesson learnt. My suggestion - they do fine together, but get the least aggressive triggers first, then add the more aggressive triggers after. They don't seem to like any 'new' fish in their space, but as long as fish were in there first, they are ok.