I have a small 5" red tiger oscar in a 29 gallon tank. I had a 8" koi in there with him and the koi got beat up on....so I'm guessing I got ahold of an uncommonly aggressive oscar. I took the koi out and put him in my other 29 gallon tank where he is much happier, but since I took him out, the oscar has been spending a lot of time just bottom sitting and appearing to be miserable. I did some reading about it and it seems that he might be unhappy with just a small pleco in the tank with him. So I am looking to possibly get him 1 or 2 tankmates. I have done large amounts of research here and on other websites and I can't seem to find any one species that everyone agrees will work. The most common fish I read might work are jack dempseys, green terrors, midas, severums (sp?), clown loaches and convicts. I am worried about the breeding power of the convicts, so I am not really interested in those fish, but I would love to have any of the others. I would also like to own a flagtail prochilodus or some datnoids....would either of these fish be okay to add in there? Please let me know what fish you think would work out well, why and what size I should start one off in the tank at (due to the fact that the oscar will grow very fast). Also, I realize this is a small tank, but its just a starter tank for the moment and the oscar, as well as all the other fish that are in there, will go into a much larger tank (125+ gallons eventually). Thanks for any and all advice!!