Blind Cave Fish

1 Species Overview

The blind cave fish is a very special ornamental fish, one that has no eyes. Its ancestors lived mostly in caves, the deep sea, or muddy waters, and over generations the fish lost its sight. Some blind fish are even born with eyes that soon disappear.

Also known as: Astyanax jordani

Class: Actinopterygii

Species: A. jordani

Chinese name: Blind cave fish

Family: Characidae

Distribution: Native to Mexico; also found in the Americas, Europe, Africa, and Asia

Phylum: Chordata

Kingdom: Animalia

Genus: Astyanax

Order: Characiformes

2 Appearance and Physical Traits

The blind fish is actually a general name for all eyeless fish. Its ancestors originally had eyes, but after living in dark conditions for a long time they gradually lost their sight, which is why later generations are born without eyes.

The blind fish belongs taxonomically to the family Characidae, genus Astyanax. It is a very beautiful ornamental fish, about 8 cm long, covered in bright silver scales, with all fins a creamy color. Tens of thousands of years ago, the ancestors of the blind fish were carried by currents into underground caves with little or no light. Over long ages, their eyes degenerated from lack of use and became the blind fish of today. For most animals, losing the eyes would be fatal, yet although the blind fish’s eyes have lost their function, it relies on the special senses of other organs to live normally. It is a fast swimmer that moves freely through the water without bumping into plants, rocks, or other fish. In short, the loss of eyes has brought no real disadvantage to its life.

3 Habitat and Living Environment

Because the blind fish has no eyes, it looks very special. What should you watch for in its captive environment?

The blind fish is native to Mexico and has become a commonly kept tropical fish as well as a subject of interest to zoologists. In captivity it is not demanding about water quality and grows well at 20 to 32 C. It can be mixed with other tropical fish of similar needs, but if space allows it is best kept alone in its own tank. The blind fish is not picky and likes to feed in the dark.

4 Feeding Guidelines

For most animals, living without eyes is impossible, but the blind fish, though its eyes have lost their use, relies on the senses of other organs to live normally. Because of its small size, feed it live daphnia.

The blind fish can be bred in captivity. The water should have pH 6.8 to 7.4, hardness 7 to 11, and a temperature held around 26 C. A breeding tank of about 80 by 40 by 40 cm is best. First pick a well-colored male and a plump female and keep them apart for a week, feeding them measured amounts of daphnia. Shortly before dusk on the day before breeding, move the pair into the prepared tank, whose bottom is lined with a layer of Java moss.