These tiny fish are thought to be Dwarf Lampeye of the Fluviphylax genus in the Killifish family.
They are native to small ponds, swamps and drainage in northeastern South America (Amazon/Orinoco Basins area). The reason for the "Lampeye" name is evident.
They are some 2-2.5cm long. Males are orange-red.
Females are grey-black. They give birth to live young.