Heterandria formosa

Aquarium fish: Heterandria formosa (Heterandria formosa)
Size: 3.5 cm
Origin: America
Water temperature: 20-26 ° C
Aquarium volume: 15 l

Heterandria formosa (Heterandria formosa ) – one of the smallest viviparous fish in the world, belongs to the beautiform family and is often found in aquarium farms.


North America. It lives in still or calmly flowing, sweet and brackish waters in the United States, from South Carolina to Louisiana. Found in shallow, densely overgrown places.

Characteristics and disposition

The smaller male is only 2 cm long, the female is much larger and grows up to 3.5 cm.

Clearly marked dimorphism. The male is slimmer and his anal fins are transformed into a gonopodium. The body of the fish is fusiform, gray-olive in the upper part, light belly. A darker strip runs along the body, from the snout to the base of the tail. There is a dark spot on the gently rounded dorsal fin.

A very mild-mannered and hardy species. It spends most of its time in the upper and middle parts of the aquarium. Unlike other livebugs, they are not prone to eating offspring. It’s best to keep them in a larger group.

Nutrition and feeding

Omnivorous and unrefined fish.

In their natural environment, they eat plankton and insect larvae, while in an aquarium they accept most of the food they give. They can be fed good-quality dry chunks, regularly giving small live or frozen foods, such as eyelash, daphnia or brine shrimp. Plant food plays an important role in their diet, they are eager to nibble on algae in the aquarium, if not enough, you can give food with spirulina.


They are perfect for the recently popular nano aquariums. A 15-liter aquarium , densely planted, well-lit, filtered, but with not too strong water movement is enough for a pair of small specimens .

The heater is not necessary. They withstand a wide range of temperatures, including really low temperatures, even 6 ° C. However, the most suitable range is 20 – 26 ° C. In warmer climates, in summer, they can be kept in backyard ponds. Due to their size, males are not recommended for general aquariums.

It will be food for larger fish. It will lose the food competition with more vigorous species. It is best to keep them in a larger group in a species aquarium, with mild fish of similar size or with non-predatory microbes, cuiras or otos .


Reproduction is very easy and even difficult to prevent reproduction if there are fish of both sexes in the aquarium. Water parameters are not very important as long as they are within the recommended range.

For example, when the water temperature values ​​are too extreme, the gender balance among the offspring may be disturbed. Small pieces are best multiplied in a group of several females and several males. Compared to other viviparous species, their reproduction is slightly different. The male courtship is limited only to chasing a pregnant female and mating with a gonopodium. The male’s milk flows along the gonopodium furrow into the female’s fallopian tube, where the mature eggs are fertilized.

Part of the sperm remains in the fallopian tubes and fertilizes the maturing eggs gradually. Thanks to this, the female can give birth to offspring several times without the male being involved again. The eggs in the female body mature gradually in batches, and the development of individual batches takes about 25 – 35 days, depending on the conditions. In one female at the same time, up to 9 batches of eggs can mature at different stages of development. As a result, it is capable of shedding offspring at shorter intervals than other viviparous animals.

Usually it gives birth every 2 – 10 days, from 1 to 11 fry. After birth, the young are large enough to immediately accept e.g. brine shrimp larvae. They grow very quickly and after about 35 days they can be fully sexually mature.


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