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Encyclopedia / Tetras / Mexican tetra
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Variations

2 kinds · tap one for a closer look

Mexican tetra

Astyanax jordani · Astyanax mexicanus, Blind cave tetra, Blind cavefish, Cave tetra

Peaceful and active mid-water schooler.

Catalog of Fishes now splits Astyanax mexicanus: the blind cave fish sold in shops is A. jordani and the sighted Texas fish is A. argentatus. Most books still call both A. mexicanus.

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12 cmAdult size ✓
20–25 °CTemperature ✓
6.5–8pH ✓
72 LSmallest tank ✓
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Not recommended
  • They need different temperatures (20–25 °C vs 26–30 °C). No setting suits both.
Not recommended
  • Oscar eats animals up to about 12 cm. Mexican tetra only grows to 12 cm.
Not recommended
  • They need different temperatures (20–25 °C vs 27–30 °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: 24–25 °C.
Compatible
Compatible
Compatible
Compatible
Compatible

317 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 ✓5–25 dGH
Group size ✓4 or more
Temperament ✓Peaceful
Swims at ✓Middle
Care level ✓Easy
Diet Omnivore
Lifespan ?Unknown
Size in shops 3–5 cm
Growth Medium

Behavior

Peaceful and active mid-water schooler.

Food

Flakes, pellets and frozen foods.

Tap a food to see what it is.

Male or female

Females are larger and fuller-bodied, especially when full of eggs; the male's anal fin has a slightly curved edge, the female's is straight.

Health

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

Breeding

Egg-scatterer · Easy

Easily bred, prolific egg scatterer; spawns overnight over mesh that keeps the adults from eating the eggs.

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 about 1,000 eggs per female; they hatch in around 24 hours and fry are free-swimming 5-7 days later.

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

RegionNorth America – southern Texas (USA) & eastern Mexico
Rivers and lakesRio Grande and Pánuco basins, and caves of the Sierra de El Abra
HabitatRivers, springs and limestone caves
Native rangeAbout 700 km across
See it on the world map

The story of the mexican tetra

The blind cave tetra of the aquarium trade descends from fish collected in Mexico's Cueva Chica cave in 1936 and is now farm-bred in huge numbers in Asia. It has lost its eyes and pigment and finds its way with its lateral line. It can interbreed with the sighted silver surface form; most researchers treat both as one species, Astyanax mexicanus, but the Catalog of Fishes now splits them (cave fish A. jordani, Texas and north-east Mexico surface fish A. argentatus).

Italian zoologist Filippo De Filippi described this tetra in 1853. Besides the normal river form, it has blind, pinkish cave populations in northeastern Mexico that evolved from river-dwelling ancestors. Both forms are kept by aquarists, and the cave form is a major model in evolution research.

First described by Filippo De Filippi in 1853.

  • Cave populations have lost their eyes and most of their pigment.
  • It is the northernmost member of the characin family.
  • Several cave populations lost their eyes independently of each other.

Sources

16 facts checked with sources