I was at an LFS a few weeks ago and watched the interaction between a pr of cons and an oscar that were sharing a tank. The cons who were much smaller than the oscar, one of the cons kept the oscar away from his space with out any problems. So I was thinking I could add one of my breeding pair of cons into my 90G that houses my oscar. I figured I would get some input before proceeding with this, I figured this would reduce my need to house fry because it would give the Oscar a in tank supply but the cons are brutal when guarding their fry so I am actually more worried about the oscars safety.