Cave tetra, blind tetra (Astyanax mexicanus) care guide

Group
Freshwater fish
Other names
Blind cave tetra, Blind cave fish, Astyanax jordani, Astyanax fasciatus mexicanus, Sardinita mexicana, Blind cave characin
Family
Acestrorhamphidae (American tetras; formerly Characidae)
Origin
Southern USA (Texas, New Mexico) through Mexico to Guatemala, in streams, rivers, pools and springs. The eyeless form lives only in caves in Mexico.
Water
freshwater
Maximum size
9.5 cm
Temperature
20–25°C
pH
6.5–8
Hardness
Medium to hard, 5–25 dGH
Minimum tank
72 litres
Care level
beginner
Temperament
peaceful

Care

A hardy, easy fish and a good choice for beginners. The blind cave form is the one most often sold; it is produced in huge numbers on Far Eastern fish farms. It grows to around 9.5 cm, larger than most tetras, so give it a tank with a base of at least 80 × 30 cm, and more room for a group. Keep at least four together. The blind form needs no special décor and navigates perfectly well by sensing small changes in water pressure with its lateral line. It can live in an ordinary planted community tank, or you can set up a cave-style tank with rockwork, a dark substrate and dim lighting, which shows it off nicely. This is a cooler-water, adaptable fish: around 20–25°C, pH 6.5–8.0, and anything from fairly soft to hard water. It does not need a heater in most centrally heated homes. Regular water changes and good filtration keep it in good condition. Blind cave tetras in the trade descend from fish collected in 1936 from the Cueva Chica cave in Mexico, and today are mostly bred commercially in Asia. Sources: Seriously Fish (seriouslyfish.com/species/astyanax-mexicanus/); FishBase (fishbase.se/summary/Astyanax-mexicanus.html); Wikipedia (en.wikipedia.org/wiki/Mexicantetra). Checked October 2026.

Diet

Not fussy. Feed a quality dried food as the staple, with plenty of small live and frozen foods such as bloodworm, Daphnia and brine shrimp. The blind form finds food by smell and its lateral line, so make sure it gets its share in a busy tank.

Breeding

A prolific egg scatterer; a female can lay up to 1,000 eggs, and the adults will eat them. Use a separate tank with a mesh, marbles or a mat of fine-leaved plants on the bottom so eggs fall out of reach, and remove the adults after spawning. Eggs hatch in about 24 hours and the fry are free-swimming after 5–7 days. Start them on infusoria, then move to Artemia nauplii. Females are larger and fuller-bodied; males have a slightly curved anal fin, while the female's is straight.

Compatibility and tank mates

Generally peaceful, but it can nip tankmates when food goes in, so avoid slow, long-finned fish such as fancy guppies and Siamese fighters. Best with robust fish of similar size that are happy in medium-hard water, such as larger danios, barbs and other sturdy tetras.

Last updated 4 October 2026. Community-edited care guide on Aquatic-Auctions.

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