Aquarium species profile

Least Killifish

Heterandria formosa · North America (southeastern USA — Florida to North Carolina)

Minimum tank5 gal

Adult size1.2"

Care levelEasy

TemperamentPeaceful

Temperature65–80°F

pH range6.5–8.0

Diet

Omnivore – micro pellets, baby brine shrimp, micro worms, algae

Compatible tank mates

Nano fish, shrimp, micro rasboras; excellent shrimp tank fish

Tank mates to avoid

Any fish larger than 1.5 inches (will eat them or be eaten)

Care notes

One of the smallest vertebrates in the world and the smallest fish in North America. Despite its common name, it's a livebearer (superfetation — carries multiple stages of embryos). Great for nano tanks and shrimp setups.

Check the whole aquarium. Tank size alone does not establish compatibility. Confirm adult size, water overlap, social grouping, territory, diet, and the individual animals before stocking.

Check compatibility in Fishician