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Heterandria formosa (Dwarf Mosquitofish, Least Killifish)

Silvery-green with a prominent black band running from the nose to the caudal peduncle. Males and females similar in colouration, but the male is smaller and has the modified anal fin typical of the Poeciliidae. Both sexes have a black spot on their dorsal fins, but only females have a similar black spot on the anal fin as well.

One of the smallest of all known vertebrates, males are less than 2.5 cm in length, and females no more than 3.5 cm. Despite their small size they are lively and quite boisterous. An excellent fish for the smaller aquarium, but because it is so small choose tankmates with care.


Fish information (behaviour and breeding):

An active, surface-dwelling fish that is naturally found in ditches and other thickly vegetated waters of the southern United States (specifically the Carolinas, Florida, and southern Louisiana). Inhabits fresh and brackish water.

Best kept in a single-species given its small size. Does not harm plants, and in fact requires ample floating vegetation to feel secure. Quite nervous and shy, particularly when newly introduced to the aquarium. If you must add tankmates, choose peaceful, small species that stay close to the bottom, such as Corydoras habrosus.

Feeds primarily on algae and small insect larvae; readily accepts flake food.

Breeding is straightforward and essentially similar to breeding guppies or any other small livebearer. Females can produce up to six broods per mating. They generally do not molest newborn fry, but floating plants will help the fry avoid their parents. Fry are dropped periodically over a long period rather than in single batches, so expect to see one or two fry every few days.

Family Group: Livebearers
Distribution Southern United States
Temperature 20-26 C
Size Up to 2.5 cm (males); 3.5 cm (females)
Water Parameters Hard, alkaline water essential; also does well in brackish water
Water PH 7.0-8.0
Diet Adaptable
Care Level Easy
Water Chemistry More than pH 7 - Alkaline
Sociability Peaceful
Schooling Fish Yes

Shop stock

The latest shops to have this fish stocked in-store are listed below. Click on a shop name for full shop details, or click the link below the shops to view ALL shops that stock this fish.

Wholesale Tropicals London E2 0AA View shop

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