Cool little jacks. I think they will all work together great in the 55 for a good while, minus the african. Red zebras can get pretty aggressive and territorial, and if you get lucky and the jacks happen to pair up, you'll have issues there.. If they're both males, you might have some issues there too.. Time can only tell though. Being that the barbs and jd's seem to be pretty close in size, I think as they all grow, it shouldn't be a problem. Why not throw some stuff in the small tank for the time being, so they can get more comfortable while they wait?