ummm ya dbcd314 said it pretty well. iv heard of one person doing this with his 2 sennys and within the first afternoon his tiger oscar had bitten one of the 6" senegals in half. personally i wouldnt recommend it but im not gona say it absolutely cant work, cause i dont know that it cant. from personal experience one of my very good friends had an oscar for a long time and back in highschool he feed it a live mouse, it riped the mouse in half. so you can understand why i am hesitant to encourage senegals with oscars. you know the temperament of your fish better than i do, he might be peaceful.. i have a betta that is unusually peaceful and gets along just fine in my community tank. you could always do a trial run, buy a cheap senegal shaped and sized fish - as close as possible - and drop it in there with the oscar and see what he does. id give a week too just to be sure everything would be ok. good luck.