Nannostomus mortenthaleri, commonly known as the coral red pencilfish, is a freshwater species of fish belonging to the characin family Lebiasinidae.[3] It is one of the most colourful of the genus, being suffused with a bright coral red colouration over its entire body and fins, in striking contrast to its horizontal jet black stripes. It was originally described as a subspecies of Nannostomus marginatus, but it is now recognised as a species in its own right.[2] Mature males have a thickened anal fin. Maximun length is 29mm.[2]
Reference from Wikipedia