This may or may not be the case with yours, but when I got mine, I didn't see him eat either, I had an infestation of Aiptasia, I would see him in the early morning and when the lights went out, going around and pecking at the rock and coral bases. I never really noticed a decreased number of Aip.(probably a month in and remember I had them everywhere), until one day it dawned on me, that is what he was doing in the morning and at night, and since then it has basically eradicated them from my system. So just keep an eye on it, if you see it being active when the lights are out(room lights on though, sometimes) or in the morning, that just may be what it is up to. Good luck with it, I hope mine continues to do well, I think it has been in the tank for over 4 months now, and it does seem to eat the other frozen food I feed the fish(Emerald Entree and frozen cyclopeze, sometimes some vitamins mixed in(maybe once a week at reduced bottle recommendations)). Good luck with yours, I hope it does the trick for your problem.
Matt
