Nannostomus Unifasciatus

Datasheet

General Description

The One-Lined Pencilfish, scientifically known as Nannostomus Unifasciatus, is a peaceful species belonging to the family Lebiasinidae within the order Characiformes. It showcases a unique oblique swimming style, distinguishing it from other congeners. With a maximum size of 4.0cm, this fish is often recognized by its slender body and characteristic color patterns, making it a popular choice among aquarium enthusiasts.

Aquarium Setup

For optimal care, the One-Lined Pencilfish should be housed in a heavily-planted aquarium with a dark substrate and floating vegetation, providing areas for congregation. The tank should contain driftwood branches and dried leaf litter to support microbe colonies and offer a secondary food source for fry. Consider gentle filtration, such as an air-powered sponge filter, to maintain water quality within the acceptable parameters of a pH range of 4.0-7.0, water hardness of 18-179ppm, and a temperature between 23-28°C (see table).

Behaviour

Although very peaceful, the One-Lined Pencilfish is not the ideal community fish due to its small size and timid nature. It is best kept with similarly-sized characids, peaceful catfish species, or as a dither fish for dwarf cichlids like Apistogramma Spp. This species tends to exhibit gregarious behavior, thriving in groups of 10 or more where aggression is dispersed, and natural behaviors are observed. Unlike some relatives, males of the One-Lined Pencilfish rarely engage in harmful sparring activities.

Feeding and Diet

In the wild, the One-Lined Pencilfish feeds on tiny invertebrates and zooplankton. In an aquarium setting, they readily accept dried foods but should also be offered small live or frozen fare such as Artemia nauplii and Moina. Providing a varied diet ensures the health and vitality of this micropredator species.

Reproduction & Dimorphism

Breeding of the One-Lined Pencilfish in captivity is not well-documented, with reports mostly attributed to the closely related Nannostomus eques. Sexual dimorphism is noticeable in adult males, appearing more colorful, slim, and possessing an enlarged anal fin. Similar to N. eques, this species likely deposits eggs on the underside of plant leaves during reproduction.

Habitat and Distribution

Nannostomus Unifasciatus is indigenous to the upper Amazon basin in countries like Brazil, Bolivia, and Colombia, as well as the upper Orinoco system in Colombia and Venezuela, and rivers in Guyana. It thrives in slow-moving tributaries, flooded forests, and swampy areas rich in aquatic vegetation and submerged structures. Exhibiting a preference for habitats with slow currents and abundant woody debris, this species coexists with various other fish species in its natural environment.