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Encyclopedia / Tetras / Red-eyed tetra
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Variations

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Red-eyed tetra

Arnoldichthys spilopterus · African red-eyed tetra, Arnold's tetra

Peaceful; needs a lid.

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10 cmBody length, without tail ✓
24–27 °CTemperature ✓
6–7.5pH ✓
108 LSmallest tank ✓
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Tank mates
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Not recommended
  • White cloud mountain minnow needs cool water and makes a lot of waste, while Red-eyed tetra is tropical.
  • They need different temperatures (24–27 °C vs 14–22 °C). No setting suits both.
Not recommended
  • Giant gourami eats animals up to about 10 cm. Red-eyed tetra only grows to 10 cm.
Not recommended
  • They need different temperatures (24–27 °C vs 10–22 °C). No setting suits both.
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

330 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 ✓1–15 dGH
Group size ✓10 or more
Temperament ✓Peaceful
Swims at ?Top
Care level ✓Easy
Diet Omnivore
Lifespan ?Unknown
Size in shops 4–6 cm
Growth Medium

Behavior

Peaceful; needs a lid.

Food

Flakes, pellets and frozen foods.

Tap a food to see what it is.

Male or female

Males are slightly more colourful, have dark stripes in the anal fin and are slimmer than mature females.

Health

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

Breeding

Egg-scatterer · Moderate

An egg scatterer, not difficult but rarely attempted. Condition with live and frozen foods, then put the best male and fattest female in a small, dimly lit tank with a mesh base and some plants, in soft water below neutral pH. The fish spawn side by side after vigorous driving by the male.

Pairing

Keep a group of 8-10 and move a well-conditioned trio or group to a spawning tank.

Setup

30-40 L tank with a spawning grid or dense java moss, soft to medium water (pH 6-7.5), a sponge filter and subdued light.

What starts it

Heavy live-food conditioning, then a water change with slightly cooler water in the morning.

Eggs

Up to 1,000 eggs per female; they hatch in about 30-34 hours.

Raising the fry

Start with infusoria or powdered fry food, then newly hatched brine shrimp; sort by size as they grow.

Common mistakes
  • Leaving adults with the eggs
  • Poor conditioning of the parents
  • Overfeeding the fry tank
Full breeding guide, day-by-day plan and simulator →

Where it lives in the wild

RegionAfrica – southern Nigeria (Niger Delta & coastal rivers)
Rivers and lakesNiger Delta and coastal rivers of southern Nigeria
HabitatSlow, sometimes murky lowland rivers and swamps
Native rangeAbout 250 km across
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The story of the red-eyed tetra

An active, large-scaled African tetra with a red upper eye and silver body, endemic to a small area of Nigeria (lower Niger and Ogun rivers). Despite being common in the hobby it is scarce in the wild and is listed as Endangered by the IUCN (assessed 2019).

George Albert Boulenger described this fish in 1909, and its genus was later named after Johann Paul Arnold, a German aquarist who helped popularise many new species. It is the only member of its genus. Its large shimmering scales and red-topped eyes make it one of the most attractive African tetras.

First described by George A. Boulenger in 1909. Named for Genus named after German aquarist Johann Paul Arnold.

  • It is the only species in the genus Arnoldichthys.
  • The upper half of its eye is bright red.
  • Its large scales shimmer with gold, blue and green tones.

Sources

16 facts checked with sources