When tropical fish hobbyists think about killifish, their first thoughts are probably about the Aphyosemion group from West Africa. The name Aphyosemion means "fish with a banner" and that suggests that these species are very colorful.
The Aphyosemion group ranges from Senegal and Gambia in the north down to Zaire and possibly Angola in the south. Most species are confined to rain forest habitats but some have adapted to the savannahs of West Africa. This extensive range has produced an incredible variety of species and populations. Because the Aphyosemion group is so large, scientists have found it helpful to divide it into subgenuses.
The subgenus Chromaphyosemion is one of my favorites. It contains just eight named species: bivitattum, bitaeniatum, loennbergi, lugens, poliaki, riggenbachi, splendopleure, and volcanum. However, these eight species are represented by over 170 known, different populations! Scientists have already found that some similar appearing populations are reproductively isolated and, when crossbred, produce infertile offspring. It is possible that many of the 170 different populations may prove to be new and distinct species.
The Chromaphyosemion subgenus primarily inhabits the lowland rain forests from Togo to Gabon, concentrated mainly in Nigeria and Cameroon. Most species live 2-5 years and grow to about two inches, but A. riggenbachi is a "giant" and can reach three inches. Like most Aphyosemion species, they prefer temperatures in the low to mid 70s, but I have kept several populations in the 80-82 degree temperature range during the summer without any noticeable problems.
Two features distinguish the subgenus Chromaphyosemion. First, most, but not all, Chromaphyosemion species display two lines running horizontally most of the length of the body. This is where the popular name "bivitattum" (or "two-lined") originated. Secondly, in many populations of Chromaphyosemion the males develop long streamers or extensions of their caudal, dorsal, and anal fins, which, coupled with their bright array of colors, can be quite stunning.
If male killies are the gorgeous peacocks of the pond, with many populations displaying distinctive and unique color patterns, their female counterparts resemble the mud. Female killifish generally exhibit a basic brownish or grayish body with little other coloration. Females of most populations of Chromaphyosemion usually display the characteristic two horizontal lines, which makes them one of the more attractive female killifish. Even so, females look so much alike that it is almost impossible to differentiate females from two or more populations. For this and other reasons, such as breeding, most killinuts carefully keep their species and populations separate.
Most Chromaphyosemion species are easily bred. Because of their size, a pair or trio can be bred and permanently maintained in tanks as small as two gallons. My favorite set-up is to keep one or two pairs in a two gallon plastic tank with a snap-on lid (killies are great escape artists). In these tanks, I add usually add either a sponge or small box filter and a spawning mop. For some species, I will add a little peat moss or coconut fiber to darken the bottom. This conditions the water, serves as an additional spawning site, and may also provide a hiding place for shy or harried adults or fry.
When the adults lay their eggs in the spawning mop, I hand pick the eggs and incubate them in plastic trays (I use a "nuts and bolts" storage unit that has 12 trays). I add enough acriflavine to slightly color the incubation water. The eggs take about two weeks to hatch. When they hatch or look like they are ready, I transfer the eggs and/or fry to Cool Whip tubs (the bigger sizes work best) or plastic shoe boxes.
As a tip, I've had better success when I add Ramshorn snails to the fry containers. The snails do not appear to bother any unhatched eggs and may actually help the hatching process. In addition, the snails may help maintain the water quality by removing the leftover baby brine shrimp and they may provide for the growth of infusoria, another fry food.
Another tip: develop a steady source of baby brine shrimp. You will see a tremendous increase in fry survival and their growth. Even adult killies appreciate baby brine shrimp and I use it as my primary food for both the fry and their parents. Most killies do not require live foods, but live foods seem to be particularly important with the fry. For killies in five gallon tanks and larger, I also supplement their diet with a variety of flake foods. As the fish become larger, flake foods become a greater part of their diet.
When you use small containers, you must watch the water quality. With hatching trays and rearing tubs, you will need to make regular water changes. Fry tend to be suspectible to shock, so small, frequent water changes are best.
Another approach that works well when spawning Chromaphyosemion is to house them in a "permanent" set-up. Typically, this is a five to ten gallon aquarium that is well planted. These tanks are eye-pleasers and the fish are only one component. Breeders have two choices: leave the fry in with the adults and let them fend for themselves, or remove them. When left in with the adults, some fry will usually survive and reach maturity. Removal can be achieved without disturbing the tank very much. Rapidly dip a container into the floating plants. The fry tend to hide near the surface in the plants and can be easily caught. After collecting, transfer them to a rearing container.
Where and when possible, I like to keep Chromaphyosemion adults in single species groups. If I have extra adult and a spare five or ten gallon aquarium, I like to establish a breeding colony. This increases the genetic diversity and can spread around any aggression by a dominant fish.
Temperature control can be a major problem with small containers. It just isn't practical to heat each tank, much less each tub. Most killinuts develop a small area for their hobby such as a closet or small room. In my case, I've built a small fish room with R-21 insulation inside my garage. During the winter I've used a thermostatically controlled portable space heater with satisfactory results.
Summer temperatures in the Sacramento Valley were my greatest challenge. Most killies will not survive prolonged exposure to 80 degree plus temperatures. For ten years I have struggled with a fan, turning off the lights during the hotter hours, and opening up the fish room and garage during the cooler hours in the morning and evening. Finally, I ran a duct from the air conditioner into the fish room. On those 100 degree plus days, it made ahuge difference!
If you enjoy colorful aquarium fish, consider killifish. I can strongly recommend the Chromaphyosemion group as a good starting place.