Description
Least Killifish – Heterandria formosa
The Least Killifish (Heterandria formosa) holds the title of being the smallest livebearing fish in the world. Despite its name, it is not a true killifish but a member of the Poeciliidae family. This nano fish is loved for its tiny size, peaceful demeanor, and suitability for small aquariums.
Introduction
- Common Name: Least Killifish
- Scientific Name: Heterandria formosa
- Size: 0.5–1 inch (1.2–2.5 cm)
- Lifespan: 2–3 years
The Least Killifish is a delightful addition to nano and planted tanks. Its tiny size and charming behavior make it a favorite among aquarists who enjoy small, peaceful species. Despite its delicate appearance, this fish is hardy and adaptable, thriving in a variety of setups.
1. Natural Habitat and Behavior
- Habitat: Native to the southeastern United States, the Least Killifish inhabits slow-moving waters such as swamps, ditches, and ponds. These environments are typically filled with aquatic vegetation, providing shelter and feeding grounds.
- Behavior: Least Killifish are peaceful and active swimmers, often found near the middle to lower levels of the aquarium. They are social fish and do best in groups of six or more.
2. Aquarium Setup
- Tank Size: A 5-gallon tank (19 liters) is sufficient for a small group, though larger tanks allow for more natural behavior and additional tankmates.
- Substrate: Sand or fine gravel works best, mimicking their natural habitat and supporting live plants.
- Decor: Add plenty of live plants such as Java moss, hornwort, or floating plants to provide cover. Driftwood and leaf litter enhance the natural look and support beneficial microorganisms.
- Water Conditions:
- Temperature: 68–78°F (20–26°C)
- pH: 6.0–7.8
- Hardness: 5–20 dGH (soft to moderately hard water)
- Lighting: Low to moderate lighting is ideal, especially in a planted tank where plants provide shaded areas.
3. Diet and Feeding
- Diet: Least Killifish are omnivorous, feeding on small invertebrates, algae, and plant material in the wild. In aquariums, they thrive on a mix of high-quality micro-pellets, crushed flakes, and live or frozen foods like baby brine shrimp, daphnia, and microworms.
- Feeding Schedule: Offer small amounts of food 1–2 times daily. They have tiny mouths, so ensure the food is appropriately sized.
4. Compatibility with Other Fish
- Tankmates: The Least Killifish is a peaceful species that pairs well with other nano fish and invertebrates. Suitable companions include:
- Celestial Pearl Danios
- Ember Tetras
- Dwarf Corydoras
- Shrimp species like Cherry or Amano shrimp
- Avoid: Larger, boisterous, or aggressive species that may outcompete them for food or view them as prey.
5. Common Challenges and Tips
- Breeding: Least Killifish are livebearers, with females giving birth to a few fry at a time rather than large batches. They do not typically eat their fry, making breeding relatively straightforward in a planted tank.
- Water Quality: While hardy, they prefer stable water conditions. Regular water changes (20–30% weekly) and careful monitoring of parameters are essential in smaller tanks.
- Overcrowding: Due to their small size, it’s easy to overcrowd a tank. Stick to recommended stocking levels to maintain water quality.
Conclusion
The Least Killifish (Heterandria formosa) is an excellent choice for nano tank enthusiasts and those looking for a peaceful, low-maintenance fish. Its unique reproductive habits, adaptability, and social nature make it a fascinating addition to any freshwater aquarium. With proper care, this diminutive species will thrive and bring life to your tank.
