Cnesterodon carnegiei, commonly known as Carnegie's toothcarp, is a species of poeciliid native to southeastern Brazil and Uruguay.

The base color is a grayish yellow, the belly is white, and the middle of the flanks show three to five black comma-shaped streaks.

Although this species is not overly sensitive, it can be an aquarium fish that feels at home even in the smallest aquaria.

Diet is not a problem as long as the aquarist realizes that these fish can only manage to swallow the smallest morsels.

After a 24 days gestation period, from five to ten, and rarely up to 15, young are born, each measuring 2 to 2.5 mm (0.08 to 0.10 in).