Mexican Tetra

The Mexican Tetra is one of the most scientifically fascinating fish in the aquarium hobby, being the only tetra with both a surface-dwelling sighted form and a cave-dwelling blind form within the same species. In its normal form, it is a robust, attractively silver-bodied fish with a slightly compressed shape and a bold personality. The blind cave form is eyeless and pinkish-white, having lost its eyes and pigmentation through evolutionary adaptation to permanent darkness. Both forms are popular in the hobby for different reasons — the sighted form for its hardiness and wide parameter tolerance, and the blind form for its scientific novelty. Native to river systems of Mexico and southern Texas, the Mexican Tetra is adapted to a wider range of water conditions than most of its South American relatives, tolerating harder, more alkaline water and cooler temperatures. This makes it particularly suitable for community tanks where tropical conditions cannot always be maintained. It is generally peaceful but may occasionally nip the fins of long-finned or slow-moving tankmates, so careful selection of companions is advised. A schooling species that appreciates groups of six or more.

Tank Setup An 80-liter tank with robust plants or artificial decor suits this active species. The blind cave form benefits from a sparsely decorated tank with smooth surfaces and no sharp objects. Both forms appreciate moderate current and good oxygenation.

Water Parameters pH 6.5–8.0, temperature 18–25°C, general hardness up to 20 dGH. Unusually tolerant of harder, more alkaline water and cooler temperatures compared to most tetras. This adaptability makes it one of the most forgiving species in the family.

Feeding An enthusiastic omnivore that accepts virtually any food including flakes, pellets, live, and frozen foods. Feed twice daily. Will eat smaller tankmates if they fit in its mouth, so choose companions carefully.

Tankmates Generally peaceful but may fin-nip. Avoid long-finned species such as fancy guppies or angelfish. Good companions include similarly sized, robust community fish: danios, barbs, corydoras, and other tetras.

Schooling Keep a minimum of six to reduce any fin-nipping tendency.

Health and Maintenance Extremely hardy and disease-resistant. Tolerates a wider range of conditions than most tetras. Regular water changes of 25–30% weekly maintain best health. A very long-lived species under good care.