Finescale Four-eyed Fish

Geographical Origin and Habitat: Anableps microlepis is found along the northern coast of South America, from the Orinoco River delta in Venezuela to the Amazon River mouth in Brazil. It inhabits shallow brackish waters, mangrove swamps, muddy estuaries, and tidal flats where it stays near the shoreline.

Taxonomy and Morphology: Belonging to the family Anablepidae, this species is named for its horizontal eye split, creating two pupils in each eye for simultaneous air and water vision. It has an elongated, cylindrical body covered in very small scales and can reach a length of 12 inches (30 cm).

Social Behavior: Highly social, schooling fish that spend their entire lives swimming right at the water surface. They are active during the day and are easily startled, often leaping out of the water to escape perceived threats or predators.

Coloration and Sexual Dimorphism: Body coloration is olive-brown to silvery-gray with a pale belly. They are livebearers exhibiting unilateral specialized reproduction: males have a modified anal fin called a gonopodium that bends either to the left or right, mating only with females whose genital openings match.

Aquarium Setup: Requires a wide tank with a large footprint rather than depth (at least 120 cm length and 400 liters). A tight-fitting lid is absolutely critical as they are exceptional jumpers. Decorate with a sandy substrate and smooth roots, leaving the surface completely unobstructed.

Diet and Feeding: Surface-oriented carnivore. Feed live and frozen foods that float, such as crickets, fruit flies, bloodworms, brine shrimp, and floating pellet foods. They rarely consume food once it has fallen to the bottom.

Water Quality: Best kept in brackish water conditions with a specific gravity between 1.005 and 1.012. Maintain temperatures at 24-28°C (75-82°F), pH 7.5-8.5, and hard water. Good biological filtration and regular water changes are essential to prevent accumulation of wastes.

Compatibility and Cohabitation: Peaceful but will consume any fish small enough to fit in their mouths. Best housed in a species-only group or with large brackish tankmates like archerfish (Toxotes), mudskippers, and silver monos (Monodactylus).

Aquarium Breeding: Viviparous (gives birth to live young). Breeding requires matched pairs of compatible lateral orientation. After a gestation period of around 2 months, the female releases 10-30 large, fully developed fry (about 4 cm long) that require immediate feeding.

Risks and Diseases: Highly susceptible to bacterial skin infections and columnaris if kept in freshwater long-term. Physical damage to their protruding eyes from rough decorations or jumping accidents can easily lead to blindness or fatal infections.