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Mexican Tetra (Astyanax mexicanus)

Welcome to our detailed exploration of the Mexican Tetra, a fascinating and popular fish in the aquarist community. This article aims to provide comprehensive insights into the world of Mexican Tetras, from their unique physical characteristics to their care requirements in a home aquarium.

Mexican Tetra Facts

Fact Details
Scientific Name Astyanax mexicanus
Common Names Mexican Tetra, Blind Cave Fish, Blind Cave Tetra
Natural Habitat Rivers of Northern Mexico and Texas
Size Up to 12 cm (4.7 inches) in length
Life Span Typically 3-5 years
Diet Omnivorous – Includes flake food, brine shrimp, daphnia, and bloodworms
Water Conditions Prefer soft, slightly acidic water; Temperature 20-25°C (68-77°F)
Behavior Peaceful; good for community tanks
Breeding Egg scatterer, no parental care
Special Features Cave-dwelling varieties are blind and lack pigmentation

Mexican Tetra Profile

The Mexican Tetra, scientifically known as Astyanax mexicanus, is a small freshwater fish native to the rivers of Northern Mexico and Texas. This species is renowned for its resilience and adaptability, thriving in a variety of environmental conditions. Interestingly, some populations of Mexican Tetras have evolved into cave-dwelling forms, known as the blind cave fish, which lack eyes and pigmentation.

Mexican Tetra Coloring

Surface-dwelling Blind tetra fish display a charming silver color with a translucent body, making them a visually appealing addition to any aquarium. The wild-type fishes often exhibit a subtle pink or gold hue, with a prominent horizontal dark stripe running along the side of their body. The cave-dwelling variety, however, is completely devoid of color and eyes, displaying a unique phenotype that intrigues many enthusiasts.

Mexican Tetra Fish Habitat

The Mexican Tetra (Astyanax mexicanus) is native to the fresh waters of Northern Mexico and Texas. These fish predominantly inhabit streams and rivers, often in areas with moderate current. They are known for their adaptability to various water conditions, including clear, murky, and even cave environments. The cave-dwelling varieties have evolved to thrive in total darkness, losing their eyes and pigmentation over generations.

Mexican Tetra Aquarium Setup

Creating an ideal environment for the Blind Cave tetra in an aquarium involves several key considerations. This section will guide you through tank size, water conditions, decoration, and maintenance, ensuring your Blind Cave fish thrive.

  • Tank Size and Type

A minimum tank size of 20 gallons is recommended for Blind tetra. These active swimmers appreciate space to move around. A larger tank also helps in maintaining stable water conditions, which is crucial for the health of the fish.

  • Water Conditions

Blind Cave tetra thrive in soft, slightly acidic water. Ideal water parameters include a temperature range of 20-25°C (68-77°F), pH levels between 6.0 and 7.5, and water hardness of 5-12 dGH. Regular monitoring of water parameters is essential to keep your fish healthy.

  • Filtration and Aeration

A high-quality filtration system is vital to maintain clean and oxygen-rich water. Choose a filter with an adjustable flow rate, as Mexican Tetras prefer a gentle current. Aeration can be achieved through the filter’s water disturbance or by using an air stone.

  • Aquarium Decoration

Decorating the tank with a mix of plants, rocks, and driftwood not only enhances its aesthetic appeal but also provides hiding spots for the fish, creating a more natural and stress-free environment. Live plants are particularly beneficial as they help to maintain water quality and provide additional oxygen.

  • Lighting

Moderate lighting is sufficient for Mexican Tetras. If you have live plants in the aquarium, ensure the lighting supports their growth while not being too intense for the fish.

  • Tank Maintenance

Regular maintenance, including weekly water changes of about 25%, is crucial. Keeping the tank clean and the water parameters stable will prevent the build-up of harmful toxins and promote the well-being of your Mexican Tetras.

Mexican Tetra Breeding

Breeding Mexican Tetras is a fascinating process that requires specific conditions for success. This section provides a detailed guide on creating the right breeding environment and understanding the spawning process.

Breeding Environment

To encourage Blind tetra to breed, set up a dedicated breeding tank. This tank should be at least 10 gallons and should have softer, slightly acidic water with a pH between 6.0 and 7.0 and a temperature slightly higher than the main tank, around 26-28°C (79-82°F). Dim lighting and the presence of fine-leaved plants or a spawning mop will provide ideal conditions for egg laying. A sponge filter is recommended to keep the water clean without posing a threat to fry.

Conditioning the Breeders

Before breeding, condition the adult tetras with high-quality food, including live or frozen foods like brine shrimp or bloodworms. This enhances their health and increases their likelihood of successful breeding.

Spawning Process

Blind cave tetras are egg scatterers, meaning they release their eggs into the water rather than depositing them in a specific spot. During spawning, the female will scatter her eggs among the plants or on the substrate, and the male will fertilize them externally. It’s common for Mexican Tetras to spawn in the early hours of the morning.

Post-Spawning Care

After spawning, it’s essential to remove the adult fish from the breeding tank to prevent them from eating the eggs. The eggs usually hatch within 24-48 hours. Initially, the fry are extremely tiny and should be fed with infusoria or commercially available liquid fry food. As they grow, they can be gradually introduced to larger foods like baby brine shrimp.

Mexican Tetra Diet & Feeding

Mexican Tetras are omnivores and are not particularly fussy eaters. A balanced diet for these fish should include high-quality flake food, as well as frozen or live foods such as brine shrimp, daphnia, or bloodworms. Regular feeding in small quantities is preferred to maintain optimal health and water quality.

Blind Cave Tetra Compatibility

These tetras are generally peaceful and make great companions for other similarly sized and tempered fish. However, their compatibility with other species should be carefully considered, especially in a community tank. They do well with other small, peaceful fish but might nip at the fins of slow-moving or long-finned species. Ideal tank mates includes Colombian Tetra, Buenos Aires Tetra, Silver tip tetra, Silver dollar, Danios, Platies, Mollies and Corydoras Catfish.

Mexican Tetra Common Diseases

Blind cave fish, like many freshwater fish, are susceptible to common diseases such as Ichthyophthirius multifiliis (Ich), fin rot, and fungal infections. Ich presents as white spots on the body and fins, while fin rot causes the edges of the fins to appear ragged and discolored. Fungal infections typically manifest as cotton-like growths. Good tank maintenance and water quality are crucial for prevention and early treatment is vital for recovery.


The Mexican Tetra fish is a versatile and captivating species suitable for both novice and experienced aquarists. Their adaptability, interesting behavior, and relatively easy care make them a delightful addition to any freshwater aquarium. By providing proper care and a suitable environment, you can enjoy the dynamic presence of these charming fish in your aquatic world.