Four-eyed fish
Anableps anableps
The fish with simultaneous vision above and below water: each eye is horizontally divided into two lobes — the upper part sees in air, the lower underwater. A unique adaptation in the animal kingdom. Surface predator in brackish waters of Central and South America. Males have the gonopodium oriented right or left — a female with compatible genitalia is needed! Livebearer. Long tank with wide surface and brackish water. Gregarious: groups of 4–6+. Lid mandatory: jumper.
Température de l’eau
24 - 28 °C
Valeur du pH
7.5 - 8.5
Type d'eau
Eau douce / Eau saumâtre
Niveau dans le bac
Surface
Taille adulte
30 cm
Volume minimal du bac
>= 200 L
Groupe minimal
>= 4
GH
10 - 25 dGH
KH
5 - 12 dKH
TDS
200 - 495 ppm
Conductivité
313 - 773 uS/cm
Description de l'espèce
Geographical Origin and Habitat: Abundant along the Atlantic Ocean coasts in northern South America (Trinidad and Tobago, Brazil, Venezuela). Frequents brackish water lagoons, mangrove swamps and the turbid water of estuaries with strong tidal influences.
Taxonomy and Morphology: Famous all over the world as the Four-eyed Fish. Its protruding eyeballs are physiologically cut in half, allowing it to see clearly both in the air and underwater simultaneously. Large species (up to 30 cm / 12 inches) with an appearance similar to an amphibian or a skiff.
Social Behavior: Strictly gregarious fish (schools of 6-8 individuals) that lives its entire existence flattened against the surface of the water. Hyper-reactive, it flees with prolonged jumps in the air (skimming) at the slightest sign of visual danger, shaken by the predatory instinct of sea hawks or herons.
Coloration and Sexual Dimorphism: The back is flat and opaque olive gray to blend in with the mud seen from above; whitish flanks mottled by opaque purplish stripes. It is a livebearer fish: males possess a huge tubular gonopodium ("dextral" or "sinistral"), females are distinctly more colossal.
Soins, reproduction et cohabitation
Aquarium Setup: Requires huge aquariums (or better marine/brackish paludariums), mainly wide and long, with very little water column (15-20 cm / 6-8 inches). Set up real mud/sand beaches and artificial mangrove banks on which they will love to rest dry, partially emerging from the water.
Diet and Feeding: Formidable surface insectivore. The basic diet consists of live crickets (baby or medium size), midges and mealworms left to float on the water, as well as shrimp and floating stick feeds (koi pellets). Will ignore anything that sinks.
Water Quality: Strictly a BRACKISH water fish. The prolonged use of fresh water will cause serious and lethal skin and fungal pathologies. Maintain a specific SG between 1.005 and 1.015 using marine salts (not table salt!). Hard waters and strongly alkaline pH (7.5 - 8.5).
Compatibility and Cohabitation: Ideal in a multispecific brackish paludarium. Can cohabit on the bottom with Periophthalmus (mudskippers), Scatophagus argus, Monodactylus or mangrove pufferfish and giant Mollies. Will instantly swallow guppies or small insects/fish.
Aquarium Breeding: Very peculiar: mating is lateral and possible only between a "right-handed" male (gonopodium bent to the right) and a "left-handed" female (genital opening on the left), or vice versa. It is livebearing: the female gives birth to 10-15 huge pups (up to 5 cm / 2 inches) ready to jump and hunt.
Risks and Diseases: Exceptional and lethal jumper: it will bang against the cover glasses breaking its snout and the delicate upper corneal lens; for this reason, it is essential to keep the water level at least 20 cm (8 inches) below the lid or net.
Origine et répartition géographiques
Abundant along the Atlantic Ocean coasts in northern South America (Trinidad and Tobago, Brazil, Venezuela). Frequents brackish water lagoons, mangrove swamps and the turbid water of estuaries with strong tidal influences.
Origine
Océans tropicaux et récifsAmérique du Sud hors AmazonieAmérique centrale et CaraïbesEurope, Méditerranée et Asie occidentale
Profil de poisson
- Tempérament
- Peaceful
- Anableps anableps is generally a peaceful and social schooling fish that thrives in the company of its own kind. However, they are naturally timid and easily startled, which can cause them to dash erratically around the tank. They are predatory toward small tankmates, meaning any fish small enough to fit in their mouths will likely be eaten. For this reason, they are best kept in a species-only setup or with similarly sized, peaceful brackish species.
- Régime alimentaire
- Insectivore
- In the wild, their diet consists of terrestrial insects, small crabs, microalgae, and other surface invertebrates. In the aquarium, they should be offered a varied diet composed of high-quality floating foods, as they rarely feed from the bottom. Gut-loaded fruit flies, bloodworms, brine shrimp, and krill are excellent high-protein options. Supplements containing Spirulina or other algae should be included to replicate their natural intake of macroalgae.
- Espérance de vie
- 6-8 years
- Taille adulte
- 30 cm
- Ratio des sexes
- Group
- These fish are highly social and must be kept in groups of at least six, preferably a dozen or more, to reduce stress and nervous behaviors. They do not form strict pairs, and stocking a mixed-sex group is ideal for natural interactions. Interestingly, their reproductive organs are laterally specialized, meaning individuals are either "left-handed" or "right-handed." This unique anatomy means a larger group increases the likelihood of compatible breeding pairs.
- Fréquence d'alimentation
- Twice daily
- It is highly recommended to feed this species twice daily to mimic their natural tidal feeding patterns. Because they are active surface feeders, food should be offered in small portions that float long enough to be consumed. Overfeeding must be avoided, as uneaten food will quickly pollute the water and degrade water quality. Consistent, regular feedings help support their high metabolism and reproductive health.
- Charge biologique
- High
- Anableps anableps is a relatively large, active species that produces a substantial amount of biological waste. To handle this high bioload, a robust and efficient filtration system, such as a large canister filter or sump, is absolutely essential. Frequent water changes are also necessary to maintain the pristine water quality these fish require. Neglecting filtration can quickly lead to dangerous rises in nitrate levels, which negatively impacts their health.
- Courant
- Strong
- These fish prefer a moderate water flow at the surface to simulate the tidal movements of their estuarine habitats. While they benefit from gentle currents that distribute heat and keep water clean, strong currents that sweep them away must be avoided. The setup should include quiet zones or resting platforms, such as flat rocks or wood extending above the waterline. This allows them to rest out of the main current when they choose to beach themselves.
- Risque de saut
- Yes
- Anableps anableps has a powerful leap and is an exceptional jumping hazard in the home aquarium. In the wild, they jump onto mudbanks and stilt roots to escape predators or hunt prey, and this behavior is easily triggered in captivity if they are startled. A secure, tight-fitting lid is absolutely mandatory to prevent them from leaping out of the tank. Additionally, a gap of humid air should be left between the water surface and the lid to protect their skin and eyes.
- Reproduction
- Viviparous
- Anableps anableps is a viviparous species, meaning they give birth to fully-formed, free-swimming young. Breeding in captivity is highly possible but requires a compatible mixed-sex group due to the lateral specialization of their reproductive organs. Gravid females have a gestation period of about 12 weeks and can become territorial and aggressive just before giving birth. The newborn fry are quite large, measuring 40 to 50 mm, and can immediately consume baby brine shrimp and crushed flakes.
- Compatibilité et compagnons
- Peaceful
- They are best housed in a species-only display due to their specialized brackish water requirements and timid nature. If kept in a community tank, they should only be paired with peaceful, active estuarine species that share their salinity needs. Suitable tankmates include sailfin mollies, monodactylus, and bottom-dwelling brackish gobies. Aggressive surface-dwellers like archerfish should be avoided as they will outcompete Anableps for food.
- Niveau dans le bac
- Top
- This species is strictly a surface-dwelling fish that spends almost its entire life in the top few inches of the water column. Their specialized eyes are adapted to look above and below the surface simultaneously while swimming at the interface. They cannot remain submerged for long periods and will naturally bob back to the top like a cork if pushed under. Therefore, aquariums with a large surface area are much more important than tank depth.
Modèles et paramètres scientifiques
FishBase
Fenêtre sur les données scientifiques officielles de l’espèce
FishBase v25.04Données synchronisées le : 15/06/2026
- Niveau trophique
- 3,3 ± 0,46 se
- Résilience
- Moyenne (1,4 - 4,4 ans)
- Singularité phylogénétique (PD50)
- 0.625
- Relation bayésienne longueur-poids
- a = 0.00537, b = 3.17
- VulnérabilitéVulnérabilité faible (20 / 100)
Galerie d'images
Images sous licence liées à l'espèce ou, lorsqu'elles sont indiquées, au taxon représentatif le plus proche.
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