ARK - Arizona Rivulin Keepers

The Gardneri Killifish: A Longtime Favorite

by Allan L. Semeit

Back in 1970, while visiting my favorite aquarium store, Mel’s Rainbow Aquarium in San Carlos, CA, some attractive, active, unusual fish mesmerized me. They turned out to be killifish and I have been enchanted by them ever since.

In those days, there weren’t many varieties of killifish in the hobby. The most common, and you had to know which rocks to look under to find them, were species known as Aphyosemion australe, Aphyosemion bivittatum, Cynolebias whitei, and Aphyosemion gardneri. There wasn’t much known about keeping killifish and this was a time of trial and error. As you might suspect, the few species we had were precious. Yet, perhaps surprisingly, the early members of the Bay Area Killifish Association were known for their generosity as well as their willingness to share ideas and technques.

One of my early favorites was Aphyosemion gardneri from Akure, Nigeria. This species was different from the other known killies in that it produced two color "morphs" or patterns: yellow and blue. The males of both morphs showed a blue body with red spots. The difference was that the yellow morph had bright, vivid yellow colors on their dorsal, anal, and caudal fins while the blue morph males displayed white instead.

Aphyosemion gardneri challenged aquarists with understanding the genetics of morphs. From breeding experiments, we learned that the yellow morph was the dominant pattern and that the blue morph was recessive. Somewhat similar to the albino recessive trait, the blues were more delicate and harder to raise. At that time, we tried to keep the two color morphs separate and develop "pure" strains. For the breeder, there was a major challenge in that the females show no color and there was no way to differentiate them by morphs. I believe our efforts for "purity" may have led to genetic deterioration, particularly with the blue morph, which became more and more difficult to raise.

Like many species of killifish, Aphyosemion gardneri has experienced some identity problems. Most of my older aquarium hobby books labeled this species as Aphyosemion calliurum (a different species having a brownish body color). Both of these species are about the same size and shape, and both are found in eastern Nigeria and northwestern Cameroon. When you consider that preserving fish causes them to lose their colors, you can understood the dilemma and confusion facing scientists who had never seen the different species alive.

The years following my introduction to killifish have seen a flood of new species and subspecies. Scheel, in Atlas of Killifishes of the Old World, states that there are fifteen named forms in the gardneri species group. He also comments that reproductive isolation has developed between many of these. Crossbreeding different populations can produce sterile hybrids, so it is important for hobbyists to know what strain they have – and not to mix them. With all of the females looking virtually the same, this can be critical! Interestingly, the Akure population is still the only one I know of that produces different color morphs.

A few years ago, scientists revised the families and genera of killifish. All of the Aphyosemion species which were considered to be semi-annual (or "switch") spawners were moved to a new genus called Fundulopanchax. Since the gardneri group fell within this category, their correct scientific name changed to Fundulopanchax gardneri.

What is a semi-annual or "switch" spawning killifish? These are species that live in habitats that may dry up some years and yet stay flooded in others. To adapt to these conditions, these killifish lay eggs that can successfully incubate either in water or when kept in or on damp peat or a similar substrate. Generally, these species reproduce stronger offspring when the eggs go through a short "drying" period of peat incubation.

My middling success with gardneri species over the years probably reflects my dislike for handling eggs requiring peat storage. Rather than remove and store the eggs, I would provide the parents with a peat-bottomed tank, let them spawn in the peat, and either remove the fry when they hatched or periodically move the parents to another tank. This approach has enabled me to produce enough fry to keep the strain going and produce some extra pairs as well.

My success with Fundulopanchax gardneri changed in 1993. At a BAKA meeting, Dr. Phil Beck from Modesto mentioned that he had recently obtained a prolific strain of gardneri from Howard Gibbs. I decided to try them and the result shocked me. These gardneri laid their eggs at the TOP of my spawning mops. Other gardneri populations always preferred the bottom portion of the mop. My second surprise was the quantity of eggs produced – I was inundated! Most of the eggs proved to be fertile and hatched after about two weeks of straight water incubation. For a while, I had fry all over the place. Eventually I had to stop collecting eggs - or look for a larger home.

This particular species of gardneri comes from Nsukka (or N’sukka), Nigeria. It does not show any yellow coloration and has a darker body than most gardneri – sort of a greenish color. Steffen Hellner, in his book Killifish, published by Barron’s, has a picture of this species on page 27. Nsukka Gardneri, as it is sometimes referred to, is an attractive species and has proven popular at aquarium society auctions. It grows to about three inches and males exhibit some short extensions on the top and bottom of their tail fin. I have found the adults to be much less aggressive toward one another than other gardneri strains and I like to keep about a dozen breeders in a ten gallon aquarium. They also enjoy flake foods.

What else can I say, except try them.