For future reference itís almost impossible to help someone with out tank parameters, size, etc. in general for most fw
eels they have a very hard time adapting to new tanks, so if it was recently shipped to the fish store then transferred to your tank it was probably to much stress for the eel. How did you acclimate the eel to your system? Itís best to add new fish to your aquarium with lights out (especially something like an eel) to minimize stress and aggression from the other tank mates.