Lucania goodei or the Bluefin Killy, as it is called, is one of the smaller and more colorful of the native killifish. Bluefin males seldom exceed 2 to 2-¼” with the females a little smaller. The body of L. Goodei is elongated, minnow-shaped making it more akin to a minnow or a Rivulus species as opposed to the stockier, bulky characteristics of Cynolebias species. The major sex differential is in the unpaired fins (as one could almost assume from the name); a blue cast on the anal and dorsal fins distinguish the males of the species.
The overall body color of the fish is brown. The fish is bisected by a dark, coco-colored, longitudinal line; beginning at the mouth, extending through the eye and ending at the caudal peduncle. Body color above this line is a lighter brown with subtle green highlights giving at times the appearance of being a hazel color. The underside is a more pale brown almost a cream color.
Blue, red and black are the small splashes of color that save this little fish from an olive-drab existence. The dorsal and anal fins are basically a vibrant, iridescent blue, tinged at their bases with varying amounts of red. All of this is enclosed in a distinctive black margin that serves to highlight the adult male who seems continually on display. The caudal fin also has its moment of color, although not as distinctive, it begins with small areas of blue at the base and then a noticeable concentration of red, which varies in intensity from a vivid red, gradually paling-out to pink and finally leaving the last quarter of the caudal translucent. All the fins of the female are void of color. Note should be made on the colors of L. goodei, it seems that the color is a variable depending on the health of the fish and the quality of its environment. I have seen this fish in poor physical condition, maintained in a crowded tank and the fish totally lacked any of the vibrant coloring after which it was named. How does the saying go: “You can’t make a silk purse from a sow’s ear”? Take good care of this little fish and it will be a “silk purse”.
My pair is maintained in a 5-gallon tank with a box filter, for aeration and a mild current which the Bluefin seems to prefer and a large mop about two inches longer than the tank is deep. The mop is dark green but that is more for my psychological well-being than that of the fishes. L. goodei are very tolerant of temperature and water conditions. My fish room can vary from the high 80’s to the low 50’s at night and I would imagine that nature would give L. goodei even further temperature extremes. Most literature says that their water should be anywhere from mildly brackish to salt, yet my pair seem to be getting along OK in fresh water. I try to feed only live foods, varying from adult and baby brine shrimp, to tubifex worms and daphnia but they have no qualms over accepting freeze-dried or flake foods as well.
In their spawning the Bluefins utilize the entire length of the mop with preference given to the upper portions, although I have collected eggs from the bottom. One strange thing I’ve noticed is that I don’t seem to get eggs daily rather I get from six to ten eggs every other day. I think it has to do with the rate or the ability of the female to ovulate successfully-because the male drives continuously, the pair embrace and enter the mop but no eggs are laid on those intermediate days.
Also as of yet, I have not noticed the need for a “wintering” period, i.e., the need to keep the fish at a lower temperature for an extended period of time to induce spawning– sort of duplicating the spring when the fish is returned to a normal temperature.
The eggs and fry are quite small but present no special problems. Eggs hatch in about 12 days at 68o and the fry can take sifted baby brine right from the start. However I prefer to start them off on infusoria and microworms for a few days and then place them on larger foods. Fry are relatively slow growers, sexable in 3 months but not fully mature until one year.
Raising a batch of “Bluefins” is rewarding in itself, they tend to be a schooling fish and make a very attractive display. Everyone should give this fish a try sort of as a “refreshing change of pace.”