How to figure out sex of the Least Killifish

How to figure out sex of the Least Killifish

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The Least Killifish (Heterandria formosa) is a species of livebearing fish within the family Poeciliidae.

The adult Least Killifish is the smallest fish in the same family with guppies, endlers and mollies.

The smallest and very cute fish with a very interesting behavior.

The adult Least Killifish females grow less than 1 inch.

Here you can see 2 young females and one male Least Killifish.

They all are young and about the same sizes yet.

Adult Least Killifish females have a fan shaped underbelly fin that often has a dark spot on it.

A fully grown adult female is one third larger than male Least Killifish.

Also, adult females have more rounded and plump body shapes as you can see here.

The shape of the underbelly fin is the easiest way to say the gender of the Least Killifish.

The adult male is on the left here has a stick shaped underbelly fin.

And Least Killifish males have streamlined body shape.

Also, males exhibit a different behavior - we will talk about in a different video.

The Least Killifish loves live food.

I have a steady supply of scuds available for them right in the aquarium you can see here.

The adult scuds grow larger than newborn Least Killifish.

All  Least Killifish babies look the same as females.

It takes a couple months for babies to grow up.

Least Killifish males mature a month or two younger than females.

Here you can see a couple month old baby Least Killifish.

At this age it looks like a tiny copy of an adult female.

Here is the big mom.

It would takes another month or so before this baby turns to be a male.

Here you can see the male with the stick shaped underbelly fin.

Have fun and happy aquariums :)