I feed my electric blue crayfish a variety of foods including:
live plants (housed 100% of the time in the tank, munches when he wants some)
live fish (I injure them slightly so he can catch them, or use a claw to hold them by him so he can grab it)
spirulina discs
bottom feeder pellots
"omega one" shrimp pellots
"small" pieces of vegetables
I leave his molt in the aquarium for him to eat, I've heard and read this gives him the calcium he needs, I also add two or three eye drops of liquid calcium into the tank once a month. (I read little pieces of eggshell is good for this as well)
I've pretty much feed him everything you can think of, only in small quantities to keep the "bad" bacteria from developing.