Bluefin Killifish (Lucania goodei)

Lucania goodei, the Bluefin Killifish, is a small and attractive freshwater fish native to Florida, USA, where it inhabits a variety of freshwater habitats including springs, streams, swamps, and coastal plains. It is one of North America's more striking native killifish, and gains its common name from the brilliant blue iridescence in the dorsal and caudal fins of mature males — a coloration that intensifies dramatically during courtship and breeding.

Males display a golden to olive-green body with a dark lateral stripe and vivid blue to iridescent fins with orange at the base of the dorsal. Females are considerably less colourful, with a plainer olive-brown body and transparent fins. The size difference is minimal — both sexes reach approximately 4–5 cm.

As a North American species from subtropical Florida, the Bluefin Killifish is distinctly cold-tolerant compared to most aquarium fish. It thrives in the 15–25°C range and can survive down to near freezing temperatures, making it an excellent choice for unheated aquariums in temperate European homes or outdoor water features in mild climates.

The Bluefin Killifish is a non-annual species — unlike many killies that survive the dry season as eggs only, Lucania goodei is a perennial fish in permanent water bodies. It spawns on fine-leaved plants or substrate, scattering eggs that hatch in 10–14 days.

Tank Setup: A 40-litre minimum for a group of six. Cool, well-oxygenated water with gentle to moderate flow. Dense fine-leaved planting (Java moss, Hornwort, Myriophyllum) for cover and egg deposition. Gentle filtration. No heater needed for most Belgian homes in typical room temperatures.

Water Parameters: Temperature 15–25°C; pH 6.5–7.5; GH 5–15 °dH; KH 3–8 °dH. Cool water is important — avoid sustained temperatures above 26°C. Moderate hardness is suitable.

Feeding: Omnivore. Feed small-sized foods: micro pellets, crushed flake, frozen Daphnia, baby brine shrimp, micro worms. Feed twice daily. Small mouths — ensure appropriately sized food.

Tank Mates: Ideal with other cool-water, small, peaceful species: White Cloud Mountain Minnows, hillstream loaches, small danios, Endler's livebearers, small peaceful North American fish. Avoid tropical fish requiring warmth above 26°C.

Behaviour: Active, schooling fish in groups of 6+. Males display to each other and females with fin-spreading and colour intensification. Peaceful and non-aggressive toward all species. Non-annual — no diapause egg storage needed for breeding.

Health: Hardy and cold-tolerant. Main risks are overheating and poor water quality. Avoid sustained temperatures above 26°C. Weekly 20% water changes maintain health.