smaller africans such as shelldwellers may be kept comfortably in a 10 but any of the more common, more colorful species, (labs, zebras, all other mbuna) deserve a 20 long IMO.
nope I cant think of a single african that would be ok for a 10gal. to small =] If you get a 20-30gallon you have a few tang. shellies you may be able to get.