Blind Cave Tetra
Astyanax mexicanus
The Blind Cave Tetra (Astyanax mexicanus) is a peaceful fish that's easy to keep. Give it a tank of at least 95 litres (25 US gallons), water held at 70-77°F, and a pH of 5.5-7.5. Always keep a group of at least 6 - they feel safest in numbers.
Captive lifespan reflects typical experience in a home aquarium, not maximum recorded age; genetics, sourcing, and care vary.
Natural distribution
Mostly South America
- South America
Regional colours match the stocking calculator's origin map.
Blind Cave Tetra Tank Setup
Give them a tank of at least 95 litres (25 US gallons). As open-water swimmers they care more about swimming length than height, so a longer tank is ideal. Keep the water at 70-77°F with a pH around 5.5-7.5, and avoid sudden swings. Always keep a group of at least 6 of their own kind - kept alone or in pairs they tend to turn shy, nippy, or wash out in colour. They reach about 12 cm as adults, so don't be misled by the small juveniles sold in stores.
What Do Blind Cave Tetras Eat?
They have small mouths, so stick to small foods: crushed flake, fine granules, and now and then a treat of frozen or live foods such as daphnia or baby brine shrimp. Anything too large simply gets ignored.
Blind Cave Tetra Tank Mates
Keep in groups of at least 6. The Blind Cave Tetra is peaceful, which is the first thing to weigh up when you choose tank mates. It's a shoaling fish, so settle a group of 6 or more of its own kind before adding anything else - a stressed, lonely fish is far more likely to nip or hide. Before you buy, run your full stocking list through our stocking calculator. It weighs temperament, adult size, and water needs together, which a single species page can't do on its own.
Are Blind Cave Tetras Good for Beginners?
Often recommended to beginners, but only after the tank is cycled and you can keep a proper school - not three fish in a new setup.
Blind Cave Tetra - frequently asked questions
What size tank do Blind Cave Tetras need?
Blind Cave Tetras need a tank of at least 95 litres (25 US gallons). A bigger tank is always easier to keep stable, and gives them more room to settle in and behave naturally.
How many Blind Cave Tetras should I keep together?
Keep a group of at least 6. Blind Cave Tetras are a shoaling species and become stressed, lose their colour, or hide when kept singly or in pairs.
What water parameters do Blind Cave Tetras need?
Keep them at 70-77°F with a pH of 5.5-7.5, steady rather than chased to an exact figure. In a cycled tank, ammonia and nitrite should both read 0 ppm, with nitrate kept low through regular water changes.
What do Blind Cave Tetras eat?
Blind Cave Tetras have small mouths, so they need small foods. Crushed flake and fine granules form the staple, with the occasional treat of frozen or live foods such as daphnia or baby brine shrimp. Feed small amounts once or twice a day, and remove anything they don't eat.
Are Blind Cave Tetras good for beginners?
Yes - Blind Cave Tetras are a good beginner choice once the tank is fully cycled and you can keep a proper group. They are hardy but still need stable water and a school to feel secure.
Common mistakes with Blind Cave Tetras
- Buying fewer than 6 - Blind Cave Tetras need a proper school to feel secure; isolated individuals hide, fail to colour up, or become stressed.
Building a community? Run the full list through the stocking calculator before you add anything else.
Great tank mates
Chosen from temperament, overlapping temperature/pH bands, plausible minimum tank footprints, and size versus yours in App-aquatic data. Hobby nuance always wins - verify stocking and temperament before purchasing.
Fish to avoid mixing with Blind Cave Tetras
These well-known species are commonly sold alongside this fish but are not recommended tank mates - verify before purchasing.
- OscarPredator - Oscar will eat or injure smaller tank mates
- Pea PufferPredator - Pea Puffer will eat or injure smaller tank mates
- Betta (Male)Predator - Betta (Male) will eat or injure smaller tank mates
