abstract:Nannostomus unifasciatus, (from the Greek: nanno = small, stomus = mouth, unifasciatus = one band), commonly known as the One-lined Pencilfish, is a freshwater species of fish belonging to the genus Nannostomus in the Lebiasinidae family of Characins. They are popular in the aquarium trade due to their small size, beautiful color pattern, unique swimming posture and relative hardiness.