The left sided livebearer (Jenynsia onca) is a small fish that is native to South America where it is found in tributaries of the lower Rio Uruguai in Brazil and Uruguay. This fish grows to an adult size of 2 to 3 inches long. Females are larger than than males. Males possess a gonopodium. Males and females are either "right handed" or "left handed" in that their reproductive organs are oriented to one side or the other. A popular myth in the aquarium hobby has it that a right handed male can only mate with a left handed female, or visa-versa. However, when actually keeping these fish, it can be seen that this is untrue. A determined male can be quite resourceful and acrobatic.
The left sided livebearer is a close relative of the four eyed fish (Anableps anableps).
The left sided livebearer prefers a temperature of 64°F to 76°F. They will do well with a pH of 6.8 to 7.8, and a hardness of up to 25°H.
left sided livebearers should be maintained in an aquarium of 20 gallons or larger. A well planted aquarium with plenty of shelter, including driftwood (ZM2000), twisted roots, and stone caves all work well. A dark colored soft, sandy substrate (CS7539) is a good choice for bringing out the best color.
The left sided livebearer is an active and fast moving fish. It should be maintained in groups of 8 to 10 with at least 2 females to every male. Rival males may chase one another, but they rarely do any damage. Left sided livebeares are prone to fin nipping, so tank mates should be chosen with care. Good choices include, zebra danios, bloodfin tetras and other streamlined tetras, swordtails, mollies, platies, and cory catfish. Avoid fish with long fins.
left sided livebearers are omnivores feeding on algae, plant matter, small aquatic crustaceans, worms, insect larvae and other zooplankton in their natural habitat. In the aquarium they may be fed dry, live, and frozen foods. Good choices include frozen brine shrimp (SF6777), live blackworms, and flakes (AL165). For maximum color, growth, and health these fish will look their best when given probiotics (AL169) in addition to a balanced diet.