Wikipedia
Lebiasinidae
The pencil fishes are a family (Lebiasinidae) of freshwater fishes found in Costa Rica, Panama, and South America. They are usually small and are known as ornamental fishes in aquaria, including popular fishes such as the various pencil fish and the splashing tetra.
Lebiasinids are small, cylindrical fish, ranging from in adult length. They prey on insect larvae, especially those of mosquitos. The family includes the voladoras, found in high-altitude lakes in the Andes and Central America, but the other species are lowland fish inhabiting the Orinoco, Amazon, and Paraguay River basins.