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Encyclopedia / Tetras / Flag tetra
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Variations

1 kinds · tap one for a closer look

Flag tetra

Hyphessobrycon heterorhabdus · Three-lined tetra, Flag

Peaceful schooler.

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3.6 cmAdult size ✓
20–26 °CTemperature ✓
5.5–7.5pH ✓
72 LSmallest tank ✓
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Tank mates
Check your own mix →
Not recommended
  • Tinfoil barb eats animals up to about 5 cm. Flag tetra only grows to 3.6 cm.
Not recommended
  • Giant gourami eats animals up to about 10 cm. Flag tetra only grows to 3.6 cm.
Not recommended
  • Angelfish eats animals up to about 4 cm. Flag tetra only grows to 3.6 cm.
With conditions
  • Only a narrow pH range suits both: exactly 7.5.
With conditions
  • Only a narrow temperature range suits both: exactly 26 °C.
Compatible
Compatible
Compatible
Compatible
Compatible

366 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 ✓8 or more
Temperament ✓Peaceful
Swims at ?Middle
Care level ✓Easy
Diet Omnivore
Lifespan ?Unknown
Size in shops 2.5–3.5 cm
Growth Medium

Behavior

Peaceful schooler.

Food

Flakes and small foods.

Tap a food to see what it is.

Male or female

Sexually mature females are noticeably deeper-bodied and a little larger than males.

Health

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

Breeding

Egg-scatterer (rarely bred) · Hard

Egg-scattering free spawner with no parental care; well-conditioned adults spawn often, and fry may even appear in a mature tank.

Pairing

Needs a large group in mature, stable conditions; pairing is hard to control.

Setup

Roomy, planted tank with very soft acidic water (pH 5-6.5), subdued light and fine-leaved plants or a spawning mat.

What starts it

Rain-season style changes: soft cool water changes, a small temperature rise and heavy live feeding.

Eggs

50-150 eggs

Raising the fry

Infusoria then brine shrimp nauplii; survival is poor without very clean water.

Common mistakes
  • Hard tap water
  • Overcrowding the breeding tank
  • Poor water quality
Full breeding guide, day-by-day plan and simulator →

Where it lives in the wild

RegionSouth America – lower Amazon basin, Brazil
Rivers and lakesLower Amazon tributaries incl. the Tocantins
HabitatSlow, vegetated streams
Native rangeAbout 500 km across
See it on the world map

The story of the flag tetra

Also called the Belgian flag tetra: a black, red and yellow stripe along the flank recalls the Belgian flag. A small tetra of shaded forest streams in eastern Brazil's lower Amazon (Pará and Maranhão).

American zoologist Albert Ulrey described this tetra in 1894, originally in the genus Tetragonopterus. Its side stripe is divided into red, gold and black sections, like a small flag. It is a peaceful schooling tetra, also sold as the three-lined tetra.

First described by Albert B. Ulrey in 1894. Named for 'heterorhabdus' means differently striped.

  • Its stripe is split into red, gold and black sections.
  • It is also sold as the three-lined tetra.
  • It was first described in the genus Tetragonopterus.

Sources

14 facts checked with sources