Blind Cave Fish
The Mexican tetra or blind cave fish (Astyanax mexicanus) is a freshwater fish of the family Characidae of the order Characiformes. The type species of its genus, it is native to the Nearctic ecozone, originating in the lower Rio Grande and the Neueces and Pecos Rivers in Texas, as well as the central and eastern parts of Mexico. Growing to a maximum overall length of 12 cm (4.7 in), the Mexican tetra is of typical characin shape, with unremarkable, drab coloration. Its blind cave form, however, is notable for having no eyes and being albino, that is, completely devoid of pigmentation; it has a pinkish-white color to its body. This fish, especially the blind variant, is reasonably popular among aquarists. A. mexicanus is a peaceful species that spends most of its time in midlevel water above the rocky and sandy bottoms of pools and backwaters of creeks and rivers of its native environment. Coming from a subtropical climate, it prefers water with 6.0�7.8 pH, a hardness of up to 30 dGH, and a temperature range of 20 to 25 �C (68 to 77 �F). In the winter, it migrates to warmer waters. Its natural diet consists of crustaceans, insects, and annelids, although in captivity it is omnivorous.