Porcupine fish will not bother your corals, anemones, mushrooms or fish.
A few quick notes about porcupines:
-- They are slow and peaceful, which makes them an easy target for aggresive fish, such as angels.
-- They have very sensitive eyes (they hunt at night) and dislike strong lights (which can blind them), and like to rest in a shaded area during the day.
-- Their favorite food (found in most grocery stores) is: oysters, clams, mussels, crab, shrimp and squid.
LeoR