That depends on what size the aquarium is. If Convicts breed, and they do so very easily, they will defend a territory, and aggressively remove all other fish from it. Typically they will vigorously defend a 3 foot long territory, which can be placed in the middle of the tank. If you have a 6ft tank, the mix could work, though no guarantees.
You could keep one convict with some Labidochromis though, if the tank is at least 29 gallons, the bigger the better.