Cave Tetra

Astyanax jordani is arguably the most biologically famous freshwater aquarium fish, having served as a key model organism in evolutionary and developmental biology research. Originally described from the Cueva Chica cave system in San Luis Potosí, Mexico, it belongs to the same species complex as the surface-dwelling Mexican tetra but has lost both functional eyes and skin pigmentation through convergent evolution across multiple independent cave populations.

Despite its scientific fame, this fish is a genuinely easy aquarium species. It navigates perfectly using its lateral line and pressure-sensing system, locates food without difficulty, and interacts normally with tank mates. It is more tolerant of cooler water and harder conditions than most tetras and can thrive in a wide range of community setups.

Feeding is straightforward: any quality aquarium food sinking to the bottom will be found and consumed readily. The Cave Tetra is an excellent educational fish and an ideal conversation piece in any aquarium.

Water: 18–25°C, pH 6.5–8.0, soft to moderately hard (GH 5–20, KH 3–12); cool water preferred. Tank: 80 L minimum; any well-maintained community setup; no special lighting required. Feeding: Any quality flake, pellets, or sinking foods; navigates and feeds by lateral line alone. Breeding: Egg-scatterer; easy to breed; condition with live foods; spawns freely in planted tanks. Compatibility: Peaceful community fish; suitable with most medium-sized species.