o yeah i went on this oscar website with almost 100 k members and almost 1 mill post and i think thats amazing sinc ethe forum is based on one fish and anyways they said 55 is a tank limmit but 75 makes the oscar feel more happy and comfortable and easier to clean. but you can add few tank mates as well and gave a list of tank mates. one of the best tank mates was mentioned was the silver dollars. it said they add barely any bioload and are fast active and to slim for oscars to eat even when younger. it said in 75 i could get atleast three of thema nd are very easy to maintain and manage even for a person like me. they add life to aquarium and said it brings out your aqaurium more with life caus ethey active rather than a slow cruising oscar. so im getting 3-4 silver dollars and 1 tiger oscar. many people have done it on website and all the fishes lived happy lives with the occasional chase but the oscar would never get contact with those speedy giuys. and said for least amount of aggression especially if your oscar you have is especially aggressive is to raise the oscar young and the silver dollars also younger