Several species target Acropora for certain. I suppose there isn't really as much of an issue with more noxious soft corals and mushrooms, as I've kept them together before, actually. I think if you look up diet under A. nigropunctatus (and at least one other, if I remember correctly) at Fishbase, you should find those references. Beyond that, I've watched them do it--I introduced some practically dead pieces (mostly ones that were stn'ing). The puffers loved it.