yea it would depend...i know milokai has huge peacock basses with smaller poly's like a 14-18"er with some 6-8" poly...nothing happened but if the eel is way smaller than the peacock bass then its trouble...but most likely no problems...what size tank will they be in?
oh...you can keep the eel in their but if you want to keep a peacock bass to adult sizes you have to get a tank of 150-180-210/220-240 and up....they need alot of space to live happily...or just make yourself a DIY tank...which will cost you WAY WAY LESS than a brand new tank or even a used one...