I asked about the Caudos before and was told they may work. I seen them, too. That's where I looked them up from after seeing them. Pretty fish. From what I read they look to play well with others. They use the rocks more and are smaller. They don't look to need the space and sand as much as ventralis. But, are they monogamous and you can only keep 2? They are also always displaying, constantly, so would be great to look at.
ophthalmotilapia ventralis is very pretty also and I asked about them, too and was told they would be a possibility and to give it a try. They get pretty big 6" and should only have one male in the tank - from what I read. If you got these, I would probably get a small amount, 1M/3F Looks like these guys will also make a nest of sand on a flat rock, too!
Oh read this, if you haven't already on them: "Ophthalmotilapia ventralis are generally found in the transitional zone between the rocky shores and the sandy bottom around the coastline of Lake Tanganyika. While female fish spend a lot of time in shoals up in the water column feeding on plankton, dominant male fish defend territories high up among the rocks but also lower down on flat rocks. These cichlid fish do not build elaborate nests in the wild but appear to like having some sand strewn across the spawning site.
In the aquarium, a male O. ventralis is always trying to energetically persuade female fish to spawn. This would be too much for just one female fish to cope with, so purchase one male and at least three females. It is easy to tell male and female fish apart, even with subadults."