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Encyclopedia / Tetras / Blackline penguin tetra
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Variations

1 kinds · tap one for a closer look

Blackline penguin tetra

Thayeria obliqua · Blackline penguin, Penguin fish, Obliqua tetra

Peaceful school.

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8 cmBody length, without tail ✓
22–28 °CTemperature ✓
6–7pH ✓
68 LSmallest tank ✓
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Not recommended
  • White cloud mountain minnow needs cool water and makes a lot of waste, while Blackline penguin tetra is tropical.
  • Only a narrow temperature range suits both: exactly 22 °C.
Not recommended
  • Giant gourami eats animals up to about 10 cm. Blackline penguin tetra only grows to 8 cm.
Not recommended
  • Oscar eats animals up to about 12 cm. Blackline penguin tetra only grows to 8 cm.
With conditions
  • Only a narrow pH range suits both: exactly 7.
With conditions
  • Only a narrow pH range suits both: exactly 7.
Compatible
Compatible
Compatible
Compatible
Compatible

343 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 ✓0–15 dGH
Group size ✓6 or more
Temperament ✓Peaceful
Swims at ?All levels
Care level ✓Easy
Diet Omnivore
Lifespan ?Unknown
Size in shops 3–5 cm
Growth Medium

Behavior

Peaceful school.

Food

Flakes and small foods.

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Male or female

Adult females are rounder in the belly and a little less intensely coloured than males.

Health

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

Breeding

No reports of successful captive breeding were found; it is presumed to spawn like Thayeria boehlkei, an egg scatterer.

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Where it lives in the wild

RegionSouth America – Amazon basin, Brazil
Rivers and lakesAmazon tributaries
HabitatSlow, vegetated streams
Native rangeAbout 1,200 km across
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The story of the blackline penguin tetra

An Amazon tetra that swims at a head-up angle. It was the original 'penguin tetra' and is the type species of Thayeria; the fish now usually sold as penguin tetra is its close relative T. boehlkei, told apart by the black stripe, which in T. obliqua tapers upward and fades before the dorsal fin.

Carl Eigenmann described this tetra in 1908. It swims with its head tilted upwards, and its black stripe runs into the lower tail lobe, giving it the name penguin tetra. It is a lively, peaceful schooling fish.

First described by Carl H. Eigenmann in 1908. Named for Genus honours the Thayer Expedition to Brazil (1865–66).

  • It often swims in a head-up position.
  • Its black stripe runs into the lower tail lobe.
  • It is often sold as the penguin tetra.

Sources

14 facts checked with sources