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Blind Cave Tetra

Scientific Name: Astyanax mexicanus
Family: Characidae, Astyanax Clade

About the Blind Cave Tetra

Species Type: Freshwater Fish
Category: Characins

Care Level: Easy. Does well in a slightly more narrow range of water parameters and shouldn't be used to cycle an aquarium. Will eat most prepared foods. May have some specific care requirements in terms of particular water parameters, social behaviors, food items etc.

Origin: Deep underground streams in caves and caverns of Mexico and Central America.

Compatibility/Temperament: Very peaceful, a suitable companion to basic water fish such as livebearers and characins that can manage in such water. Though not a shoaling fish, it does better in small groups.


One of the larger tetra species, distinguishable by their lack of eyes and albino colouring which evolved through thousands of years living in pitch black caves where sight was not necessary. The young are born with sightless eyes but these are covered by skin and degenerate as they mature.

A peaceful species good for the community tank but an aggressive eater. Care must be taken to ensure that other fish in the community get their fair share. Being blind, it may tend to pick at other fish during feeding, but this is due to its method of searching out food, not aggression.

As with all fish, the lateral line along the sides of the body assimilates information as to the physical surroundings by detecting small changes in water pressure as it swims, and the fish is able to produce a spacial map of the environment which is quickly memorized. When placed in a different environment, it swims around very fast to gather information for a new "map."

Females are heavier bodied than males, and males have a slight curve to the anal fin. Easy to spawn in slightly basic moderately hard water. Parents will quickly devour the eggs and must be removed after spawning.

A second species, Astyanax jordani, is identical in every respect except that it has eyes and lives in streams on the surface. The two species are sometimes confused in name; and the blind species is sometimes incorrectly referred to as A. fasciatus mexicanus. The subject species was originally named Tetragonopterus mexicanus by De Filippi in 1853 but is now considered valid as Astyanax mexicanus (De Filippi 1853).

The genus Astyanax was previously considered within the Sub-Family Tetragonopterinae, but this classification has for some time been deemed incertae sedis [Latin for "of uncertain placement"]. In a study published in 2010, it was determined that the Sub-Family Tetragonopterinae should only be used for species within the genus Tetragonopterus. [Robert Javonillo, Luiz R. Malabarba, Stanley H. Weitzman and John R. Burns, "Relationships among major lineages of characid fishes (Teleostei: Ostariophysi: Characiformes), based on molecular sequence data," Molecular Phylogenetics and Evolution, Vol. 54, No. 2 (February 2010)]. Also, J. Marcos Mirande proposed several revisions to the Family Characidae based upon phylogenetic diagnosis in "Weighted parsimony phylogeny of the family Characidae (Teleostei: Characiformes)," Cladistics, Vol. 25, No. 6 (July 2009). Some genera were moved to a new Sub-Family, while others were assinged to a specific clade within the Family.

Blind Cave Tetra Diet

Omnivore. Will eat anything it can! For best health feed a variety of meaty foods, flakes and some vegetable matter. Won't consume plants but known to nibble at them.


Grows to 3.5 inches.

Minimum Tank Suggestion

36 inches in length

Ideal water parameters for Blind Cave Tetra

Slightly basic/alkaline (pH 7.0 to 8.0) and moderately hard (hardness to 25 dGH) water, temperature 20-25C/68-77F.

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