Couple of newbie questions... dumb ass starfish & food

Hi, yesterday I added my first inhabitents to my new reef/fish tank, 2
humbug damsels - doing very well and very entertaining to watch them
chase each other around the tank! 5 blue legged hermit crabs - again
doing very well and very active (these guys can really motor!) and a
red star fish, which has decided he wants to stick himself to the
underside of the condensation tray support on my tank! Depending on
what powerheads/skimmer etc. are on the water level drops, and he is
then only partially submerged in the water... is he safe there??? I
have tried to gently persuade him off but he is rooted solid to the
spot and doesn't want to move, shall I just leave him? Lastly whilst
purchasing my animals, my LFS said not to feed them on anything
intended for human consumption, and only to feed them on gamma
irradiated frozen foods (which they have a freezer full of!), are they
right? or am i safe to work on my seafood cocktail and feed them that
(which a lot of websites seem to recommend).

Any advice appreciated.

Chris.