Pencilfish

Nannostomus beckfordi

Also known as: Beckford's pencilfish, Golden pencilfish, Brown pencilfish

Water Parameters

• Temperature: 23–28°C
• pH: 5.5–7.5
• Hardness (GH): 18–143 ppm (1–8 dGH)

Values above are general hardness (GH). For carbonate hardness (KH), the buffer that keeps pH stable, see the water parameters guide.

Care Summary

A graceful, understated alternative to the usual schooling tetras, the pencilfish is a slender, pencil-thin fish that hangs and glides through the upper water in loose formation, the most popular species (Beckford's) glowing in warm gold and red with a bold dark stripe. Pencilfish have a quieter charm than flashier nano fish: they move slowly and deliberately, display to one another with subtle colour changes, and shift to a quite different barred night pattern after lights-out. Beckford's is the hardiest and most widely tank-bred of the group, making it a genuinely beginner-friendly choice, though all pencilfish have small mouths that call for small foods and a peaceful, unhurried community so they are not outcompeted at feeding. Kept in a good-sized group in a planted, gently-lit tank, they are a calm, elegant, and slightly unusual addition to a peaceful nano or community aquarium.

Tankmates

A slim, peaceful, slow-moving schooling fish that cruises the upper half of the tank, best kept in a group of at least eight, in which the males develop richer colour and display to one another with fins raised, sparring harmlessly at dawn and dusk (pencilfish change colour markedly at night, taking on a different barred pattern, which is normal). Their small mouths and gentle, unhurried nature make them poor competitors against fast, greedy fish, so pair them with other calm nano and small community species: small tetras and rasboras, corydoras, otocinclus, and dwarf shrimp, with which adults are safe. Avoid fin-nippers, boisterous fish, and anything large enough to eat them. A planted tank with floating cover and subdued light brings out their best colour and confidence.

Compatible with

• Ember Tetra
• Neon Tetra
• Harlequin Rasbora
• Chili Rasbora
• Pygmy Corydoras
• Otocinclus
• Cherry Shrimp
• Sparkling Gourami

Avoid keeping with

• Betta
• Angelfish
• Large Cichlids
• Fin Nippers
• Tiger Barb

Common Problems

• being outcompeted at feeding by faster fish
• faded colour in small groups
• needing small foods for a tiny mouth
• ich

Sources: seriouslyfish.com, fishbase.org · Last updated: 2026-06-20