I think it varries with the eel. I know when I put small guppies in my tank for other fish, the needles sometimes take a nab at them.
I would feed them live ghost shrimp as well, just put a few in the tank and they will hunt them. It's great to watch. Also, mine enjoy blood worms and small nightcrawlers (bigger ones you should cut up)
Some people say to feed them shrimp pellets, but honestly, I've never seen mine eat them.
Thats a great deal from petsmart. We got my first eel there and it was skinny, then I got two more that were easily 6" and fat. A great deal IMO as well.