Bluefin killifish

Lucania goodei

FreshwaterFish

Care at a glance

Temperature: 64–77°F (18–25°C)
pH: 6.5–7.5
Adult size: 2 in (5 cm)
Minimum tank: 11 gal (40 L)
Temperament: Mostly peaceful
Social behavior: Schooling
Swim level: Middle
Difficulty: Easy
Breeding: Easy
Rarity: Common
Origin: Southeastern USA: peninsular Florida, with sporadic Atlantic-coast populations to South Carolina and SE Alabama
Family: Fundulidae

Overview

Keep them in a group of six or more in a tank of at least 40 liters, since males color up and display best with company and dither fish nearby. They are mostly peaceful schooling fish that hold to the middle of the water column. Run the water cool, roughly 18 to 25 C, at a pH from 6.5 to 7.5, and skip the heated tropical setup since long-term warmth shortens their lives. They are micropredators, so feed small live, frozen, and prepared foods like daphnia, baby brine, and micro pellets. Pair them with small, calm, cool-tolerant tankmates and avoid large or pushy fish that will outcompete them at feeding. This is a native species, so never release them or their water into local waterways, and check your local rules before keeping or moving them.

In the wild

Bluefin killifish come from quiet, heavily planted waters across peninsular Florida, with scattered populations up the Atlantic coast into South Carolina and southeastern Alabama. Think slow springs, ditches, and weedy pond margins thick with vegetation. Give them a tank of 40 liters or more with dense planting and some floating cover, since they are a bit shy and use the plants to feel secure. Soft to moderately hard water suits them, neutral-ish at a pH of 6.5 to 7.5. They are a cool-water, subtropical fish, happiest from about 18 to 25 C, so most homes need no heater at all.

Good to know

This is a small North American killifish in the family Fundulidae, reaching around 5 cm and reported up to about 6 cm in the wild, though aquarium adults usually settle near 4 to 5 cm. It is a continuous egg scatterer that lays into fine-leaved plants over an extended season, with no parental care. A well-kept fish lives a few years, and cooler water tends to lengthen that.

Did you know

Males earn the name by flaring bright blue and red in their fins, and the color show is a group affair. A lone male stays drab, but put several together and they spend the day sparring and displaying to each other, which is when the blue really comes out.