well, from personal experience, I have had a female green terror, and jack dempsey both with my large Oscars. Now keep in mind my Os are the largest, for now, my JD is still a juvi. He is only around 4-5 inches, where my Os are around 10 inches.
I have had horrible luck with RD's, sure u know what I mean. Anything super aggressive is bad, and too small also, but then again, I have 4 baby fish in my tank and my Os dont care about them. I have 2 Salvinis in there too, they dont get too large and they are REALLY pretty fish. They can also handle their own!
I had a synsillium, he was crazy, and was no good. I also had a firemouth, seemed to be a good match, but got murdered by the syns.
You can try convicts...but try to get 2 females, not one of each, obviously keep as many males in the tank to a minimum..
Severums can get nasty to, but are pretty, try one of those out, but they grow slow, get one thats at a good enough size the O would never be able to eat it, even at full size. My sev's are small, but my Os dont mess with em, its like they know they are cichlids or something,
