Least Killifish

Heterandria formosa

Minimum Tank Size

5–10 gal

Temperature

68–78°F

PH

7.0–8.0

Adult Size

0.8–1.4 in

Temperament 

Peaceful social nano fish

Care Difficulty

Intermediate

Diet & Feeding

Provide a varied species-appropriate diet using a quality staple plus supplemental foods that match natural feeding behavior. Avoid overfeeding.

Care Instructions

Keep conditions stable around 68–78°F with suitable chemistry. Account for adult size, behavior, bioload, and escape risk where relevant.

Flow & Filtration

Use mature biological filtration and appropriate oxygenation/flow. Keep ammonia and nitrite at zero and manage nitrate through routine water changes.

Planted Tank Suitability

Plant compatibility varies with digging, grazing, size, and water chemistry. Use hardy or protected plants when necessary.

Tank Mate Compatibility

Good Tank Mates
  • Pygmy Corydoras
  • Small Shrimp
  • Tiny Rasboras

Use Caution 
  • Betta

Avoid
  • Angelfish
  • Large Fish

Compatibility Notes

Very small livebearer best in quiet nano communities or species-focused planted tanks.

Breeding Notes

Breeding strategy varies by species; provide appropriate spawning sites and separate fry or young when necessary.