In home aquaria, there are no species that can survive with e. eels. Some keepers have kept large plecos in with e. eels. But, it can be very comfortable for the cat since the eel's discharge chases substrate (mts) snails up and out of the tank.
Keeping an e eel means providing for a fish that reaches 8 feet in length. If you plan on growing one for a while and then selling it when it gets too big, keep in mind how hard it's going to be to move a large 600volt-producing sub-adult without frying yourself.