The Four-Eyed Fish
by Mercedes Calabro
The Anableps anableps is an incredibly adaptable freshwater fish. Part of the order Cyprinodontiformes, it is related to killifish and livebearers sharing a specialized organ called a gonopodium. Females max out around ten inches and the males reach around seven inches. Anableps are found in tidal waters along the South American coastline, the Gulf of Paria, and the Amazon. In these tidal conditions, their adapted eyes come in handy. Anableps have two eyes on each side of their head that sit on top of one another and allow an extended field of vision while they search for food. During low tide sneak up on small insects and crabs using the set of eyes above water and launch themselves out of the water to grab their prey. When the tide rises they use the lower set to find small fish, snails, and amphipods (microscopic scavengers) below the surface.
Anableps are fairly hardy. They need large, preferably shallow, tanks with brackish water and enjoy both open spaces to swim and built up rocks and driftwood to rest on near the surface of the water. Based on the variability of their natural habitats they can handle a pH anywhere from 7.5 up to 9.0 and like the typical tropical water temperature of seventy eight degrees. Based on the size of the tank and how many fish are present, a strong filter is needed (canister filters work well) as they produce a lot of waste.
Anableps do well mostly in species specific tanks, but are compatible with other, bigger yet peaceful livebearers, and should not be placed with other top-dwelling fish that create too much competition for food as they have no competitors in the wild. Lastly, Anableps have a wide diet including: terrestrial insects, red macroalgae, small crabs, and small fish. So in your own aquarium, there are many options to feed to recreate their natural food sources. A basic pellet should be used for most feedings, preferably one with added spirulina would be beneficial, as they eat it in the wild. Also, Bug Bites by Fluval can substitute for the insects they usually hunt in the wild. Frozen bloodworms, chopped up earth worms, and occasionally blackworms (especially if the fish aren’t interested in pellets or frozen yet) can be used a few times a week for some added nutrition. Overall, the Anableps adaptations make it a very interesting and unique fish that would be a great addition to the right aquarium.