Did you buy the eel from one of these shops? If so, you should ask them what they were feeding them. I fed mine mealworms, freeze dried bloodworms, and ghost shrimp. They will probably eat small fish.
What small dry foods were they? Most of the dry food I have is floating, but I tried some sinking catfish shrimp pellets (nutrafin) and they don't eat those either. They are crumbly, so they break up into small pieces.
with my experience fire eels love frozen blood worms... order them off line, they dont go bad.. and upload some picks the smallest one ive ever seen was like 7inch or so