My Zebra does this quite often. Its a perfectly normal and natural event IMO. What you need to remember is that eels are scavengers and in the wild theyre lucky if they eat once a week. Being in a tank with a regular feeding schedule is a big adjustment. If he wants to eat, let him. If he doesnt, try tomorrow, or the next day. It could go on and on. They will also stop feeding every couple of weeks. As long as water tests are good, they do this naturally. Everyone freaks out when thier eel doesnt eat for the second time the same day. I feed mine twice a week. Most of these posts lately are from a lack of information. Most of this is due to the fact they were not sold the animal correctly and secondly the person doesnt do any research before "impulse buying" thier next specimen. Look into these animals before purchase! Know what to expect before you buy!