F8's can eat all sorts providing they can get there teeth into it.
a full muscle in shell would be just too big, so either crush it or feed them something smaller.
i feed mine chopped musscle, cockles, prawns, clams, crab legs, snails, bloodworm, whiteworm, daphnia.. the list goes on and on.
Just make sure you give them a variety and make sure they eat something with a shell on , like a snail or crabs legs so there teeth grind down,
hope this helps.