I am planning on doing a blackwater Rio Negro biotope tank with my 29 gallon. I currently plan on having 6 Corydoras Adolfoi. I additionally want a small schooling fish, perhaps a cardinal tetra school, and also a cichlid pair. I want them to be native to the Rio Negro, but I'm not familiar with the region. What suggestions do you all have for the schooling fish and a small cichlid pair that stay small enough for a 29 gallon and won't bother the cories or the schooling fish?