Kribs? Keyholes, rams, most dwarf cichlids for that matter... Gouramies (though you'll need an extra tank to actualy spawn them in and later you can use this tanka s a grow-out for the fry and permanent home for the parents). Killifish, cories, barbs or danios (you'll need an extra tank for the parents), all sorts of livebearers, badis badis, shelldwelling cichlids, some malawi cichlids such as yellow labs... you could even breed discus if you could find a proven pair and were up for the water changes!