You need a big bruiser in that 90g tank with an eel. Can try to go for either Red Devil (A. labiatus), Jaguar (P. managuense), Midas (A. citrinellus -- the one on my avatar), three-spot (A. Trimaculatus), Red Terror (A. festae), Black belt (V. maculicauda), V. bifasciatus, V. synspilus, and many more.
Also, the eels you mention can get pretty big. I think you should get 125g tank or bigger.