Mine was getting blackworms at the LFS
and that is what I've been giving him. I tried some sinking carnivore pellets but he hasn't eaten them at all. I would like to get him to eat frozen blood worms, but I'll have to try that later.
Someone else wrote that only a stupid fish will starve to death. If they get hungry enough they should eat.
My birchir eats flake sometimes, I'm sure the eel could do that as well.