The Heterandria Formosa Fish it’s usually found in shallow, heavily-vegetated marginal areas of still or sluggish bodies of water. It can also be found in brackish conditions in some areas.
Maximum Standard Length
Male 0.8″ (2cm). Female 1.4″ (3.5cm).
A gently-filtered, heavily planted setup suits it best. Other decor can be added as you wish. Water flow must be kept to a minimum.
Temperature: It’s a hardy species, being subject to a large range of temperatures in its natural waters. Somewhere between 68-78°F (20-26°C) is best in an aquarium.
Unfussy and omnivorous, it will accept most foods offered. It’s particularly fond of small live or frozen varieties such as brine shrimp or Daphnia, and the diet should contain a good proportion of these. It will also browse on algae, so try to ensure it receives some vegetable matter in the diet. In the absence of algae crushed spirulina flakes work well.
Males are much smaller than females and possess an enormous gonopodium.
Very easy. It’s nigh on impossible to prevent it breeding if both sexes are present in an aquarium. Water parameters are unimportant, provided they are within the ranges stated above. The tank should be planted heavily. It’s best kept in a small group with several of each sex present for bredding purposes.
The gestation period is around 4 weeks. The species has a slightly different method of fry production to most other livebearers, involving a process known as ‘superfoetation’. This is defined as ‘formation or development of a second foetus when one is already present in the uterus’. Fry at different stages of development can therefore be present in the uterus of the fish at any given time. In addition, the egg yolks of the species are nutritionally poor, and the developing fry derive much of their nourishment via organs that function in a similar way to the placenta of mammals. As a result of this process, fry are dropped continually rather than in defined broods. You’ll see a few fry appearing every day or two if you have more than one female in the tank. They are quite large at birth and can accept powdered dry foods and Artemia nauplii straight away. The adults will not usually harm them.
Formosa is the smallest known live-bearing fish species, and one of the smallest overall fish species in the world. It’s not often seen for sale these days, although it’s quite widely available in hobbyist circles. When buying these, ensure they have been identified correctly as they’re sometimes confused with the much more aggressive mosquito fish of the genus Gambusia.
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