One-Lined Pencilfish

One-Lined Pencilfish (Nannostomus Unifasciatus)

The One-Lined Pencilfish, also known as Single-Barred Pencilfish, is an eye-catching freshwater species characterized by its slender body and a striking single horizontal black stripe that runs from its snout to its tail. These beautiful fish boast a golden-brown body with iridescent hues, making them a popular choice for aquarium enthusiasts.

One-Lined Pencilfish are peaceful, reaching an adult size of approximately 1.5 inches. They thrive in schools of at least 8 or more, encouraging their natural behavior and reducing stress. Suitable tank mates include other peaceful, small species like tetras, rasboras, and small catfish. Unlike their relatives, rival males rarely spar or do each other harm in any way.

As omnivores, One-Lined Pencilfish enjoys a diet consisting of small live or frozen foods such as brine shrimp, daphnia, and bloodworms, along with high-quality flake foods and micro pellets.

To create a comfortable habitat for Pencilfish, provide a well-planted aquarium with a dark substrate with subdued lighting to enhance their colors. Include hiding spots using driftwood, rocks, cavies, and plenty of live plants to mimic their natural environment. Pencilfish tends to swim in the middle and top regions of the tank; the addition of floating plants offers an additional sense of security and diffuse light. Pencilfish also requires a spacious aquarium, and their décor arranged to create plenty of broken lines-of-sight to reduce aggression between males.

These fish thrive in soft, slightly acidic water with a moderate water flow. Use a gentle filtration system; an air-powered sponge-style unit is generally adequate and performs regular water changes.

A minimum aquarium size of 10 gallons is recommended, while an ideal community aquarium size would be 20 gallons or larger. Maintain water conditions with a pH of 5.5-7.5, hardness of 3-12 dGH, and a temperature range of 73-81°F (23-27°C).

A well-fitting tank cover is also necessary, as One-Lined Pencilfish may jump when startled.
Introduce these fish into a mature, stable aquarium environment to ensure their health and well-being.