if you8 want to breed for the sake of breeding, then convicts are perfect, but if you are trying to do it for some money (by selling the fry) convicts are lousy.
You can try some south american cichlids, like the apistogramma family, they are beautiful, gorgeous, reasonably rare(well, where i am from they are), and command a pretty good price. But they prefer soft acidic water, ,which you may not have.
You could also set up a huge community fo shell dwellers like "multis" that will probably breed.