Mine took a few days of being in the tank before he would eat. Then he would only eat krill. You just gotta wait til he's comfortable and try bunches of different foods.
This is the eel in the tank with the peacock bass? You may need to put the eel in a tank by himself for a while until he starts eating and growing. That's what I did with mine. I put him in a 20 gal planted with some live ghost shrimp. (he was 6" long at that point)