Least Killfish (Heterandria formosa)

The Least Killifish is North America's smallest freshwater fish and an adorable native livebearer that thrive in numerous tiny shouls across the southeastern United States. Despite its name, it is more closely related to guppies than true killifish.

​Size: EXTRA SMALL! Males reach roughly 1.5 cm; females up to 3 cm.

​Appearance: Olive-bronze body with a bold dark horizontal stripe and distinct orange spots on the dorsal and anal fins.often found in tones of gold and occasionally a white or very light tan.

​Behavior: Peaceful, hardy, and curious. They are social fish and absolutely thrive in large numbers.

​Unique Trait: They use superfetation, meaning females can carry multiple broods at different stages of development, frequently birthing one or two fry at a time as frequently as every other day or so! 

Fun fact!: On rare occasions, they have been known to hybridize with the bluefin killfish, another native species. This creates a killfish with the head and belly of a least killie with an elongated body and horizontal stripe reminiscent of the bluefin killfish.

These tiny sweeties are a hardy, low-bioload species that thrives in quiet, vegetated setups. Their bioload is extremely low, almost non-existent, It would seem, making them very easy to keep in a nano setup in large numbers! Even having a school of fifty or seventy five of these tiny fish in a five gallon aquarium would still seem like a small school!