Based on the research I've done, to avoid being over stocked, you're going to want to limit yourself to something like a school of Mollies, Guppies, Tetra's, Pladdies, or other similar fish.
Based on a random sampling of cichlids @ Aquarium Fish: Tropical Freshwater Fish and Saltwater Fish for Home Aquariums
, their site indicates African cichlids needed 50g to 70g minimum tank size (depending upon exact bread), while there were a few American cichlids that went as small as 30g for a minimum tank size.
I don't know how accurate their information, but liveaquaria list minimum tank sizes for all the fish they sell. Seems as good a place to start researching unless someone else gives you something better.