Hmm, you know I help out aquarists on two different forums and I see this question a LOT... usually a variation on the theme, "I have no idea what to feed my fish, to which my standard reply is, "What was it eating at the LFS?" There's a lesson for all here; never purchase a marine fish that is not chowing down at the LFS; and I don't mean nibbling/tasting/picking at rocks/sampling and spitting out, etc. etc. I mean chowing down.
This is why I will never purhcase a mail order marine fish; if I can't see them eat, I don't buy them, period. If it was eating at the LFS, and you are offering the same food, then there is a good chance you have a water quality issue or other enviro problem; could be aggression or some other issue but something is usually wrong if a fish stops feeding, and it's generally considered a bad sign.