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Mexican Tetra

Astyanax mexicanus

Freshwater Central America Usually captive bred

Often kept as the eyeless, unpigmented blind cave form, this hardy characin navigates flawlessly using a highly sensitive lateral line. Highly active and boisterous, it can be an opportunistic fin nipper, so avoid housing it alongside slow, long-finned tank companions.

Also called: Blind cavefish, Mexican tetra.

9 cm adult length, drawn to scale. torpedo body.

Try it in the planner Opens a tank sized to its minimum with 6 fish added.

What it needs

ItemValueBecause
Adult length 9 cm Used for the Space check: the tank must be long enough for the fish to turn round.
Smallest tank 100 L, at least 80 cm long estimated The least water and floor length this species is kept in for good, as a single fish or smallest group.
Extra water per added fish 10 L estimated What each further fish adds once the minimum is met.
Waste load Class 2 of 5 estimated How much waste an adult makes against its size. Feeds the Load check.
Temperature 18 to 25 C Stock sharing a tank need overlapping ranges.
pH 6.8 to 8.2 Compared with tankmates in the Water check.
Hardness GH 8 to 20, KH 4 to 12 Degrees of general and carbonate hardness.
Flow Medium Low-flow fish are stressed in a strong current.
Light Dim Matched to the lighting class on the needs sheet.
Group size At least 6, ideally 10 Kept alone or in small numbers it hides, fades or turns on tankmates.
Temperament Semi-aggressive Not territorial.
Swims in Middle water Fish that use different levels share a tank more easily.
Lifespan About 8 years A fish is a long commitment.
Experience Suits a first tank A guide to how forgiving the species is of mistakes.
Jumps Yes Keep the tank covered.

Tags marked estimated are judged from the size and habits of the species rather than measured, so treat them as a sensible default.

Diet and tank layout

Mexican Tetra is an omnivore that swims in the middle of the tank. It leaves most plants alone. Give it some cover. It nips fins.

Tankmates

Works with

No close matches in the data. Check the pair tool.

Depends

Avoid

Compare any two fish on the compatibility page, or print the equipment for a stock on the needs sheet. How this is worked out: the method.