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Encyclopedia / Tetras / Three-lined pencilfish
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Variations

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Three-lined pencilfish

Nannostomus trifasciatus · Three-banded pencilfish, Three-striped pencilfish

Peaceful and shy; keep with calm tankmates.

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3.6 cmBody length, without tail ✓
24–28 °CTemperature ✓
5–7pH ✓
68 LSmallest tank ✓
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Tank mates
Check your own mix →
Not recommended
  • Tinfoil barb eats animals up to about 5 cm. Three-lined pencilfish only grows to 3.6 cm.
Not recommended
  • White cloud mountain minnow needs cool water and makes a lot of waste, while Three-lined pencilfish is tropical.
  • They need different temperatures (24–28 °C vs 14–22 °C). No setting suits both.
Not recommended
  • Giant gourami eats animals up to about 10 cm. Three-lined pencilfish only grows to 3.6 cm.
With conditions
  • Only a narrow temperature range suits both: 24–25 °C.
With conditions
  • Only a narrow temperature range suits both: exactly 24 °C.
Compatible
Compatible
Compatible
Compatible
Compatible

273 species in our list are a good match.

Facts checked against sources on 16 Oct 2026. ✓ means a source backs it; ? means no reliable source yet. See sources

Care and water

Hardness ✓1–12 dGH
Group size ✓10 or more
Temperament ✓Peaceful
Swims at ✓Top
Care level ✓Easy
Diet Omnivore
Lifespan ?Unknown
Size in shops 3–4 cm
Growth Medium

Behavior

Peaceful and shy; keep with calm tankmates.

Food

Small live and frozen foods such as baby brine shrimp and daphnia, plus fine flakes.

Tap a food to see what it is.

Male or female

Adult males are more intensely coloured, especially in spawning condition; females are noticeably rounder-bodied.

Health

Common problems. Tap one to see the signs. This is a guide, not a diagnosis.

Breeding

Egg-scatterer on plants · Hard

Egg-scattering free spawner with no parental care; spawns over fine-leaved plants, mops or mesh in soft, slightly acidic water, and adults eat the eggs.

Pairing

Keep a group with several females and condition on live foods; pairs form on their own.

Setup

20-30 L tank with soft acidic water (pH 5.5-6.5), dense fine-leaved plants or java moss, dim light and a gentle sponge filter.

What starts it

Soft acidic water, dim light and daily live baby brine shrimp; spawning is usually in the morning.

Eggs

Adults are removed after 2-3 days in the spawning tank and the first fry appear about 3 days later; first foods are Paramecium or 5-50 micron dry food. No egg count found in the sources checked.

Raising the fry

Feed infusoria, then fine fry food and newly hatched brine shrimp; fry are tiny and need very small food.

Common mistakes
  • Hard alkaline water
  • Strong flow
  • Leaving adults with the eggs
Full breeding guide, day-by-day plan and simulator →

Where it lives in the wild

RegionSouth America – Amazon & Rio Negro basins and the Guianas
Rivers and lakesAmazon, Rio Negro and Guiana rivers
HabitatSlow, vegetated blackwater streams
Native rangeAbout 1,500 km across
See it on the world map

The story of the three-lined pencilfish

A pencilfish of the western Amazon and Guyana with three dark lengthwise stripes; colour varies by population, one form sold as 'super red' for its long red stripe, and many trade fish are farmed.

Franz Steindachner described this pencilfish in 1876. Its three dark stripes and red fin patches make it one of the most colourful pencilfishes. Like its relatives, it switches to a blotchy night pattern after dark.

First described by Franz Steindachner in 1876. Named for 'trifasciatus' means three-banded.

  • Its stripes change to dark blotches at night.
  • It has three dark stripes along its body.
  • It feeds on tiny invertebrates near the surface and among plants.

Sources

16 facts checked with sources