my fire eel was only ever fed blood worms before i bought him but now quite happily eats chopped up prawn and live earthworms, one idea you could try is just to use the bloodworm to lure him out to the surface and when he gets close remove the bloodworms and hold a small piece or prawn instead and see what happens, this will also get him used to feeding from your hand. could also try seachem's garlic guard/entice, ive never used either of these products but some one on the forum may have some experience with it?