Add another small male and female. You just don't have a pair yet. Expect 1-2 fish casualties if you're not paying close attention and remove the non-breeding pair quickly. Competition drives convicts. Once there's another male/female in the tank, the dominant 2 will pair off and get about their business.
Convict Cichlids, the fact that they're in a split 10g on the other side of a fish they "know" will tear up their fry is enough to keep things from working. Given the fact you're planning to toss pond fish in a 55, step back and realize that even in a 55g, a breeding pair of convicts will eventually claim 90% of the tank, usually regardless of what's in their way. They'll still abuse and kill fish 3x their size, if they don't submit and hug the opposite wall, assuming they're in the mood.
They'd more than likely breed in the 10 if they were alone. Even then, fry would suffer if they decided to spawn again. You simply need more room.
