Nannostomus marginatus is a freshwater characin that belongs to the family Lebiasinidae. The most notable characteristic is its size: it is one of the smallest members of the genus Nannostomus.
The Dwarf Pencilfish is a pretty little shoaling species known from tributaries, backwaters, and swamplands, where the water is sluggish or almost still, and crowded with dense vegetation and an abundance of leaf litter. The water in the native habitat is very soft and acidic, and stained a tea colour from the tannins in the decaying leaves and wood.
Distribution: Amazon and Orinoco river basins: Brazil, Ecuador, Colombia, Guyana, Peru, Suriname and Venezuela.