These pelagic Cypriniformes, or in case of Lake Tanganyika Clupeiformes are very susceptible to any kind of stress. It's difficult to catch them alive and unharmed, it's difficult to transport them (still a pretty rough travel from lake Tanganyika to the airport in Daressalam). And they need a lot of space = large aquarium. And all this effort and costs for feeding them to some frontosa....