The trouble I see with the Oscar with the Convicts is that it is kind of like putting a Great Dane puppy in with a pair of Pitbulls. Yeah, the Dane is bigger, but also kind of dopey and slow. The two Pitbulls would tear him up, right? A better fit might be some of the semi aggressive cichlids like Brasiliensis (gets huge), Firemouth, Blue Acara, that kind of fish. Avoid Jewel Cichlid, Jack Dempsey, Green Terror, and the like, because they might tear up your Convicts. It's ALWAYS hit and miss when you're doing a cichlid community. I think your tank is big enough to pull it off. Just be sure to provide a ton of hiding places using rocks, driftwood, half flowerpots, and other stuff like that. I'm sure for every fish I mentioned some have had negative and positive experiences. I have kept the three I mentioned to avoid together, in a smaller tank than yours. It worked for me but I'm sure not suggesting it to you. Be sure to re-arrange the tank's decor majorly before any fish is added, and be ready to react when trouble starts. In other words, don't wait until damage is done. If one starts bullying another, assume it will escalate and remove the offender right away.
