Blind Cave Fish: The Fish Devoid of Eyes

Astyanax fasciatus mexicanus

Blind Cave Fish (Anoptichthys jordani or Astyanax fasciatus mexicanus), Mexico
Reinhard Dirscherl/Corbis Documentary/Getty Images

Living in the dark with little food and oxygen in its Mexican habitat, the Blind Cave Fish had to save its energy and being sightless allowed them to survive. A research team from Lund University in Sweden measured the energy cost of sight in the captive Cave Fish, along with vision-related parts of their brain. The results, published in the September 2015 journal Science Advances, showed that sight cost the young fish 15 percent more energy than if they were blind.

Blind Cave Fish: Basics

  • Scientific Name: Astyanax fasciatus mexicanus
  • Other Names: Mexican Tetra
  • Family: Characidae
  • Origin: Texas, Mexico, Central America to Panama
  • Adult Size: 3.5 inches (9 cm)
  • Social: Peaceful - suitable for community tank
  • Lifespan: 5+ years
  • Tank Level: Mid dweller
  • Minimum Tank Size: 20 gallons
  • Diet: Omnivore, eats most foods
  • Breeding: Egglayer
  • Care: Easy
  • pH: 6.0 - 7.8
  • Hardness: to 30 dGH
  • Temperature: 68-77 F (20-25 C)


The Blind Cave Fish is named for what it lacks -- eyes. Although totally devoid of eyes, it has an uncanny ability to navigate adeptly, apparently by bouncing sound waves off objects around them. Originating from deep caves in Mexico where the lack of light and predators made vision obsolete, they are one of most novel fish commonly available today.

Eyes are not the only feature this fish lacks. This unique fish is also without pigmentation, taking on a pink hue from the blood vessels beneath the skin.

The lack of eyes and color have not lessened its popularity, though. The Blind Cave Fish is an active, peaceful fish that's easy to care for, and it makes an interesting addition to a community tank.

Studies have been conducted to see if eye development could be stimulated. Surprisingly, when lenses from sighted fish were transplanted to the Blind Cave Fish, it began to develop an eye.

The hope is that further study of this phenomenon may prove useful in treating human blindness.


Water parameters are not critical for this fish, and it will tolerate a range of conditions from soft acidic to hard alkaline water. Likewise, water temperature is not critical and may range from the 60s to the 80s. Because it is an active swimmer, ample open space is welcomed. Lighting is not a major concern, however, it has been reported that they prefer subdued lighting.


Blind Cave Fish are as easygoing about their food as they are about their habitat. They will consume any food offered including flake, freeze-dried, frozen, and live foods. For optimum health, feed them a varied diet.


Females are somewhat larger and plumper than males, but otherwise, they have no distinguishing markings. Prior to spawning, condition fish by feeding live foods for several days. To stimulate spawning, drop the water temperature to 66-68 degrees. The female will scatter up to 100 eggs throughout the breeding tank.

Don't move the eggs as they are sensitive to handling. Fry will hatch within two to three days and be free swimming before the week is out. Feed them freshly hatched or frozen baby brine shrimp as well as commercially prepared fry foods, or very finely crushed flake foods.

Interestingly, the developing fry initially have eyes which atrophy as the fish matures.