Blind Cave Tetra

Geographic Origin and Biotope: Native to North and Central America (Texas, New Mexico, east-central Mexico). The surface form inhabits rocky streams and rivulets, while the famous blind form lives exclusively in dark underground pools and limestone caves.

Taxonomy and Morphology: Blind Cave Tetra (Astyanax mexicanus). In the aquarium hobby almost only the cave variant is known: robust and corpulent fish, totally depigmented and completely devoid of eyes, which orient themselves and hunt via a hyper-developed lateral line.

Social Behavior: Exuberant, chaotic and gregarious. Swims non-stop feeling the environment. Has no cognition of "visual territory", so it often bumps into other fish until it learns to map the tank with its pressure sensors.

Coloration and Sexual Dimorphism: The cave form is a translucent pinkish-white; the scales reflect silvery iridescence. Healthy adult females become significantly larger and rounder ventrally than males.

Aquarium Setup: Spacious tanks (min. 100 cm / 40 inches). Prefers dark backgrounds, blunt limestone rocks and sand. Light does not bother it (it is blind), but delicate plants will be destroyed by its incessant exploratory swimming. Avoid sharp decorations or pointed branches.

Diet and Feeding: Voracious omnivore. Instantly perceives food in the water. Frantically pounces on flakes, granules, bottom tablets, bloodworms and brine shrimp. Their voracity can prevent other slow fish from feeding sufficiently.

Water Quality: Exceptionally tolerant and robust. Thrives in hard and alkaline tap waters (pH > 7.5), preferably cool (20-24°C / 68-75°F). Does not require heaters in mild climates and can withstand slightly polluted waters better than other tetras.

Compatibility and Tankmates: Due to its perennial agitation and habit of "tasting" tankmates, pairing with shy or slow fish (like Angelfish) should be avoided. Ideal in active community tanks with Danios, large Barbs or moderate Central American Cichlids.

Aquarium Reproduction: Free spawner, randomly scatters eggs on the substrate. Group reproduction is easy if parents are well fed and then removed. The fry (which initially have eye rudiments that later degenerate) are robust and voracious.

Risks and Diseases: Rarely gets sick. The real problems stem from unintentional "nipping": lacking sight, they nibble on long veil fins to understand who is in front of them, causing serious damage to slow ornamental fish.