The barred pencilfish, Nannostomus espei, is a lebiasinid considered endemic to the Mazaruni River system in Guyana. The only member of the genus to show a vertically-barred pattern permanently, it has five dark bar-like markings on each flank where congeners have horizontal stripes. It inhabits sluggish blackwater habitats where pH can be as low as 4.0, and its small size and timid nature suit a tank of its own or diminutive tankmates.

Moderate