Ive found oscars are not as bad as most people say, mine have been in with jags, silver dollars, fire eel, tin foil barbs, gouramis, electric yellows, convicts,other smallish cichlids, plecs and syno's and they have never fought with anyone else (apart from the syno when it came close to eggs). Its just a matter of making sure everyone has a chance to get food as they are greedy. But we feed the fire eel by hand with 4 oscars in the tank and it def does not go hungry.