Imo basin

The blue diamond tetra, Alestopetersius smykalai, is an alestid from the Imo and Niger drainages in Nigeria. The only member of its genus found outside the Congo system, it has a prominent dark, roughly diamond-shaped marking on the caudal peduncle, and adult males lack extended median caudal-fin rays. Very rare in the hobby, it is considered Vulnerable by the IUCN because of rainforest loss, dams and habitat degradation in the Niger delta.