most pigmy Angels seem to be trouble, if not at first then down the road they can causes issues, or stress on different corals. not saying that you will see noticeable damage in most cases but non the less. nipping is just in their nature. they may not start off doing it but in time they may start. in a larger tank you may not even notice an issue all. some sps will just stop opening during the day. they may even a quire taste for soft coral and lps, but in those cases it will be very noticeable. i am i saying you shouldn't have one, not at all but i do think about the cost of some corals over a fish that may cause issue, damage, and stress to my corals.