Lol, yep, they are very well known for that kind of behavior. You will need to be sure that there are absolutely no gaps at the top of the tank. You will probably need to put some egg crate in where the AC110’s return to the tank. The eel will find its way up into the filters or worse, it will find its way out of the tank. If it’s already gotten into one of the filters, then it won’t be long until it ends up on the floor by accident.