PisciDex Species Profile
Least Killifish
Very small livebearer for mature planted nano aquariums, best kept in groups with gentle tankmates or as a species-focused colony.
Heterandria formosa
Poeciliidae | North America | Southeastern United States
Core Requirements
Tank Size
5 gallons minimum
Adult Size
1.2 inches
Group Size
Group 6+
Bioload
1/10
Water Parameters
Temperature
68-78 F
pH
6.5-8
Plant Safe
Yes
Invert Safe
Yes
Data Confidence
medium
Temperature note: Recommended and tolerated temperature ranges currently match the primary care profile.
Care Warnings
- Tiny livebearer that can be outcompeted or eaten by larger fish; best with very small peaceful tankmates or a species-focused colony.
Behavior & Husbandry
Temperament
Peaceful
Aggression
1/10
Diet
Omnivore
Difficulty
Intermediate
Lifespan
3 years
Breeding
Easy
Schooling
Yes
Compatibility Tags
CommunityNano TankPeacefulSchoolingMid WaterTop WaterPlant SafeInvert SafeShrimp SafeHardwater
Similar Species
Species Compatibility
Database-driven compatibility notes for planning community aquariums.