Fire Eels should be fed eathworms or blackworms (live), but also foods like raw shrimp - sorry that you don't want to deal with such foods, but those are what they eat... perhaps you should rehome him? I have to ask, what size tank is it in right now?
110? Cool, I was worried there because lots of places sell them small and people don't realize how big they get (2ft max). Found some more info that I wasn't aware of regarding feeding, on the linked info page of AC:
"Bloodworms and Tubifex as Juveniles, Nightcrawlers and other larger food as adults. Will eat fish small enough to fit into its mouth, so choose tankmates wisely. Will also take insect larvae, beef heart, and prawns." - An AC Post About Them