Edit Heterandria formosa

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Name

Scientific name

Heterandria formosa

Described by

Authority Girard, Year 1859

Family

Poeciliidae

Common names

Least Killifish

Photograph credits

All 2 credited

Summary

The least killifish, Heterandria formosa, is a tiny livebearer from the United States, found in heavily vegetated margins of still or slugg…

Size and aquarium

Maximum size

20mm, standard length

Aquarium size

Water movement Low: still or sluggish water

Water

Water conditions

Temperature 20–26°C, pH 7–8

Hardness

5–20dGH

Conductivity

Not recorded

Behaviour

Temperament

Peaceful

Community suitability

Not for a community

Where it lives

Countries, regions, rivers and lakes

United States, Bogue Chitto, Caloosahatchee, Coosawhatchie, Everglades National Park, Frog Creek, Greenfield Lake, Haskell Wetlands, Hatchet Creek, Hillsborough, Kanawha, Kissimmee, Lake Okeechobee, Otter Creek, Pee Dee, Santee, Shark, St. Johns, St. Louis Canal, Stanley Creek, Steinhatchee, Wakulla

Writing

Etymology

Not written yet

Distribution

Type locality is 'Charleston, South Carolina and Palatka, Florida, U.S.A.'

Habitat

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.

Aquarium size

A pair of these can be kept in a tank as small as 12" x 8" x 8" (30cm x 20cm x 20cm) - 12.5 litres.

Maintenance

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.

Water conditions

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 aqua…

Diet

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 di…

Behaviour and compatibility

Not a community fish in the general sense, although it's very peaceful. Males in particular are so tiny that they will be seen as a snack by many of the common…

Sexual dimorphism

Males are much smaller than females and possess an enormous gonopodium.

Reproduction

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 …

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.

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Where does this come from?

My own experienceFor example, I've kept twelve in a planted 60 cm tank since March 2024.A website I sawFor example, an IUCN Red List assessment, a museum catalogue or a FishBase page.A paperFor example, Marshall et al. (2011), Water temperature differences in interfluvial palm swamp habitats of Paracheirodon axelrodi and P. simulans.A book, or something not onlineFor example, Tappin (2010), Rainbowfishes: their care and keeping in captivity.Something already on the pageFor example, the Behaviour and compatibility section already says this.

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DOI

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Title

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Authors

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Year

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Pages

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Anything worth adding

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Notes

This species is also referred to as 'mosquito fish', 'dwarf livebearer' or 'dwarf top minnow' in aquarium literature. , H. formosa is the smallest known livebe…

References

No references

Name

Scientific name

Described by

Family

Common names

Photograph credits

Summary

Size and aquarium

Maximum size

Aquarium size

Water

Water conditions

Hardness

Conductivity

Behaviour

Temperament

Social needs

Community suitability

Where it lives

Countries, regions, rivers and lakes

Writing

Etymology

Distribution

Habitat

Aquarium size

Maintenance

Water conditions

Diet

Behaviour and compatibility

Sexual dimorphism

Reproduction

Notes

References

References