One-Lined Pencilfish (Nannostomus unifasciatus)

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One-Lined Pencilfish

Nannostomus unifasciatus4537.JPG
One-Lined Pencilfish

Nannostomus unifasciatus

95 Litres (25 US G.)

3.5-4 cm (1.4-1.6")




5.5 - 7.0

25 -28 °C (77-82.4°F)

4-8 °d

1:2 M:F

Pellet Foods
Flake Foods
Live Foods

3-5 years



Additional names

One-Lined Pencilfish, Oneline Pencilfish

Additional scientific names

Nannobrycon unifasciatus, Poecilobrycon unifasciatus


The anal fin of the male has red colouration, while a female's anal fin will only be white and black. Mature females are also plumper than males. These fish are tricky to breed in captivity.

Tank compatibility[edit]

A peaceful fish that must be kept in a shoal of at least 5 of its own kind. Keep with other non-predatory peaceful fish of similar size.


Should accept most foods including live/frozen foods such as brine shrimp and daphnia as well as small pellet and flake food.

Feeding regime[edit]

Feed once or twice a day.

Environment specifics[edit]

These fish require a mature spacious tank without very bright lighting. They appreciate a planted tank with floating plants to diffuse the light, combine dense planting with some open swimming space. They prefer a dark substrate to a light one. These fish can be very sensitive to water chemistry, preferring acidic water.


This is a peaceful active little fish that are known to swim at an angle. When they are stressed by water conditions their colours will fade.


A slender elongated fish which has an olive green-brown back. A fine, iridescent gold-coloured line extends from the tip of the snout, through the eye and to the caudal fin. Right below this line is a broad, black band that also extends from the snout, through the eye, and continues to the tip of the lower lobe of the caudal fin. The belly is pale cream-white. A small, black, oval spot is located on the upper lobe of the caudal fin. The anal fin is black with a white edging, while the other fins are transparent.


External links[edit]