I've kept a school of tiger barbs with my africans to act as dithers. They didnt bother them once however a buddy of mine tried to add tiger barbs and they all got killed. Up to the fish. Personally I would go with either giant danios or tiger barbs. I went with tiger barbs cause I like the hierarchy they form within their shoal lol. Also, like vinboy said, synodontis would be a perfect addition since they are from the same region. Some are really nice looking if you look around. Make sure whatever you get is fast and not small enough to be eaten/killed.