By Donna M. Recktenwalt
Color in killifish is always a good topic for animated discussion. Certainly there are enough colorful species among the Cyprinodontidae to keep even the most jaded aquarist interested. But color can vary widely, both among and within species. Especially with the annual killifish, males from the same spawn may vary widely, even when raised together under identical conditions. Such variations in color are normal; however, genetic inheritance is not the only factor affecting color in fish. Factors that may have a direct influence on the intensity of fish colors include diet, stress, and lighting.
A point to consider is which colors are of concern. Pale shades of the blue colors may be directly influenced by the amount of light the fish receives, since they are the result of guanine crystals formed in the fishes’ scales. In contrast, the reds and oranges are carotenoid-based and are directly influenced by diet. In addition, some coloration develops more slowly than others; the red or orange colors tend to take longer. And in some species, only the dominant male in a tank will color up fully, and then sometimes only when triggered by some unknown factor.
Factors Beyond the Fishroom
Using publications for reference, even those with high quality color plates, can further confuse the issue, since the skills of the photographer and printer are as influential on what is seen as were those of the aquarist. A fish that is truly spectacular may not photograph well; one that is ordinary may result in an excellent image, due to the skill of the photographer. And sometimes both the fish itself and the resulting photograph are stunning.
“I have heard people scoff at the picture of a BIT on the back cover of Hellner’s book,” says Oleg Kiselev, “saying that colors like that did not exist in real life. But I have a tank of BIT that look every bit as good and as brightly colored and as spectacularly finned. I find that the BIT look their best when they’re startled by the lights suddenly being turned on about an hour after the main lights in the fishroom are shut off,” Oleg Kiselev adds. “They don’t know quite what’s going on, so they flare up the fins and turn on the colors.”
From time to time, variants will appear within the hobby, a fish or a strain different from the usual, or a color morph, such as the Gold and Red/Orange AUS and the Gold LIN. Other variants appear, as well. In May of 1997 Monty Lehman noted that he had a pair of A. gardneri Akure in which the male “has the best greenish body color that I have seen in many, many years.” The glowing green A. gardneri do exist, confirms Sandy Binder, “or did at one time. I saw … [some] that were a glowing green. It was remarkable.” Richard Sexton reported that in 1989 Dennis Haggerty had sent him some Akure from Germany that were more purple than blue, with wide flaring caudals and extraordinary coloration.
Effects from Lighting
More commonly, the colors perceived in killifish are affected by lighting. Many fish will “bleach out” when maintained in environments that are too bright, from lack of cover or from pale backgrounds. Yet in nature many fish sport for more intense colors than those shown by even the best aquarium fish, and may endure far brighter conditions than are ever seen in a fishroom.
Many aquarists have seen their fish “glow” more than most illustrations indicate, most usually when the afternoon sunlight strikes them. The quality and intensity of this reflected color cannot be compared to the colors seen under artificial lighting systems.
The overall color of the Epiplatys species seem to directly relate to the amount of sunlight they receive. With only a few hours of sunlight a day their colors are very intense, notes one breeder. Remove the sunlight for a month and their colors fade. “They really need sunlight to bring it [the colors] out,” adds Jay Exner. The blue highlights on E. dageti Monroviae are particularly noticable; “the males’ blue eyes stand out in any lighting, just like the females’ yellow eyes.”
Jorgen Scheel, referring to Cynopoecilus ladigesi and discussing “metallic” colors, noted that males raised in tanks with strong light developed “more metallic brilliance than males that were raised in dark tanks. In the dark tanks the development of pigments on the sides of the males is more intensive than in light tanks.” This appears to be true for all rivuline males.
As Karl Johnson has pointed out, under the artificial conditions of the fishroom proper substrate and backing color can be useful in helping fish show their best. A tank well filled with plants and with a dark bottom, from dark paint, dark gravel, or a layer of peat, will usually prove beneficial. Trace elements in the peat also seem to mute the panic response in fish.
Since the color red is carotenoid-based, including more carotene containing foods in the diet can prove of benefit: color enhancing dry foods, bloodworms, or daphnia or brine shrimp supplemented prior to use. Although long regarded as an excellent substitute, frozen brine shrimp may be less effective, due to nutritional loss during the freezing/thawing process.
The Effects of Stress
Fish also tend to “pale out” when frightened or stressed. Those that are used to activity near their tanks and associate a human with being fed tend to be less frightened and to recover their normal colors more quickly when startled.
Whether destined for a sale or a show, or just for moving down the street, catching and transporting fish causes stress. A few precautions can ease its effects.
Don’t feed them for 24 hours prior to shipping, to reduce potential waste. Net the fish as quietly as possible, and transfer them to shipping bags using a container so they never actually leave the water. If they will be subject to frequent inspection and handling, try adding “cover” in the form of a strand or two of yarn or java moss, or a layer of newsprint on one side of the shipping bag, between the inner and outer layers.
— G.C.K.A. Newsletter, April 1998