Four-eyed fish

Geographic Origin and Biotope: 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.

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 Tankmates: 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 Reproduction: 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.