Blind Cave Tetra

The Blind Cave Tetra also known as Astyanax Jordani gets its common name from the fact it is blind. In the wild they live in underground caves in Mexico. This is no light in the underground caves and over millions of years these fish adapted to their surroundings by going blind.

When they are born they actually have eyes. Their eyes don’t work and as the fish gets older skin grows over its eyes and then eventually the eyes disappear completely

A recent study, which was reported in National Geographic, has made a surprising discovery. Even though these have been blind for a long time they can in fact produce fry which can see . There 29 different known types of Blind Cave Tetra. Each type of fish evolved independently within its own cave and this meant the evolution to blindness happened in a different way to each group of fish. Therefore by breading fish from different caves the faulty genes cancel each other out enabling the fry to see. Source

Behaviour and Tank Mates

They find their way around the aquarium using its lateral line They are very active fish. They are not aggressive, but they do have a reputation as fin nippers. They do not mean to harm other fish, but because they have no eyes they often mistake their tank mates as food. They also bump into other fish by accident, which can annoy the other fish. They should not be kept with aggressive fish as they will really struggle to defend themselves against sighted fish.

Tank Requirements

These fish grow to a maximum of 4 inches and like to live small groups of at least 3. Therefore I would recommend a minimum tank size of 100 litres. They are fairly adaptable regarding pH, but try to keep it between 6 and 8 pH. In their natural environment they would live in the dark, so they don’t require aquarium lighting. They don’t mind lighting and lighting does enable the fish keeper to see their fish.


These fish love their food and surprising have no trouble finding it. They will eat most food , including flake food, sinking pellets and live food. They are so fast at getting to the food and eating it, you find the other fish in the aquarium go hungry. One tactic used by fish keepers is too give them something first to distract them while the other fish eat, sinking pellets or algae wafers would be good for this as they stay in one piece. 

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