My Maroon Clown got along great with all of my other fish, but as soon as it adopted the BTA in my tank (which took a couple of months) it started being agressive. It doesn't bother the hippo or yellow tang, but it chases after the chromis' (without much success by the way). It has really gone after the percula clown though. I haven't seen any signs of damage done, the percula kind of stands up to him, but definite animosity there. I was so glad when he started hanging out in the BTA and also giving it food sometimes, however not liking the aggressiveness.