They're pretty aggressive from my experience (mine is at least). It's likely to be the boss of the tank, so adding other fish after it, when it's established the whole tank as its territory could be problematic. It may settle after it's shown them who is boss. I left mine to it, but it was added after all the other bigger fish. Things are fine now, but it still has a go at my foxface, and tangs from time to time.