(Nannostomus unifasciatus)
Nannostomus unifasciatus, (from the Greek: nannos = small, stomus = mouth; from the Latin: 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. With its long, pencil-shaped profile, its single jet black stripe reminiscent of the graphite core of a pencil, and its eraser-colored caudal fin, this is the species for which the popular name, 'pencilfish', was first coined in the 1920s, later to be applied to all the species of the genus Nannostomus.