Oscars are very flexible as far as tankmates go. You could technically do some less aggressive (yellow lab, etc...) Africans. Africans that have been farm raised really don't require the same hard water, high PH conditions of wild Africans. Most will do fine in the same water conditions as CA/SA. My stocklist with my 12 inch Oscar is a GT, JD, Vieja Argentea, Red Terror, Jag, Godmani, Firemouth, Convicts, Midas, Trimac, and a Pleco. Only the JD, GT, Con, Godmani and FM are full grown and they do great. I would not necessarily recommend the others as adults. Mine are moving tank as soon as they let me know they need to.