freshwater community4


Least Killifish

least killifish

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Scientific Name:   Heterandria formosa      
Min. Tank Size:   25 gallons      
Personality:   Peaceful      
Temperature:   68-78°F      
pH:   7.0-8.0/10-20°dGH      
Size:   1.75"      
Diet:   Omnivore      
Breeding:   Livebearer      


Should not be kept with large or predatory species; can be kept with Pencilfish, Dwarf Corydoras, Otocinclus catfish and freshwater shrimp.

Least Killifish

Also known as the Dwarf Livebearer, Least Killifish are one of the smallest species of freshwater fish in the world and they are the smallest species found in North America. These fish are native to the south-eastern United States where they can be found in shallow, densely-vegetated and slow-moving waters. They may even be found in brackish conditions. The Least Killifish can be identified by their olive coloration and the dark stripe running laterally along the body. Most specimens also exhibit a dark spot on the dorsal fin and females of the species may also have a spot on the anal fin.

Tank Set-up

Though their common name suggests otherwise, Least Killifish do not belong to the Killifish family. This species is rarely seen for sale, though they remain popular in the aquarium hobby. These fish tend to be fairly hardy, but are best kept in heavily-planted tanks with gentle filtration to keep the water flow at a minimum.


Least Killifish are an omnivorous species and, in the home aquarium, they are likely to accept any foods offered to them. Because they are omnivores, these fish require some vegetable matter in their diet, but they also enjoy live and frozen foods like brine shrimp and Daphnia. Feed a varied diet for optimum health and coloration.


Breeding Least Killifish is very easy and this species often breeds on its own when specimens of both sexes are kept together. Water parameters in the breeding tank are not important, but the tank should be heavily planted. After a gestation period lasting 4 weeks or so, these fish give birth to fry continually rather than in broods. This is because Least Killifish reproduce through the process of "superfoetation" which makes it possible for fry at varying stages of development to be present in the uterus at the same time.

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