AN INTRODUCTION TO KILLIFISHES

Richard Cox

 
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This is an introduction to keeping killifishes aimed at the complete beginner. It will be phrased in simple language without the use of technical terms unless they are fully explained in the text.

It is not a definitive composition but purely the author’s own findings based on over thirty years of keeping these beautiful and somewhat challenging fishes. That is not to say they are difficult to keep and breed. Far from it but certain species are quite a challenge until the conditions required are mastered. Rachovia pyropunctata
Rachovia pyropunctata
Firstly let us discuss what we mean by killifishes. They comprise a group of fishes of the family Cyprinodontidae and are commonly known as the egg laying tooth carps. They are found within the equatorial belts throughout the world and in practically all regions except Australasia. For the purposes of this article, in simple terms, they are divided into three distinct groups: the annuals, semi annuals and non-annuals. The annuals live in the wild for, usually, a single season in temporary ponds and swamp areas. With the onset of the annual rains they hatch from eggs deposited in the mud by the parent fishes. They then grow very quickly, maturing and breeding before the waters again dry. Semi-annuals live in areas which sometimes dry out but at other times retain water throughout the dry season. The non-annuals live in permanent bodies of water and, in some cases, will live for anything up to five years.
Nothobranchius rachovi
Nothobranchius rachovii
The types within the same groupings vary dramatically from continent to continent. The annuals of Africa, mainly a genus named Nothobranchius, vary in shape size and colour from the annual Cynolebias of South America. Such differences are to be found in other genera throughout the world. At the moment the classification of killies is undergoing many changes so I won’t dwell on this aspect in this article, as it will only tend to confuse. I can foresee, with the benefit of DNA testing, many more changes. To the beginner this is all very confusing but I can assure you that it is all very necessary. The naming of fishes is conducted in accordance with strict rules as laid down by an international body called the International Commission of Zoological Nomenclature. All scientists and taxonomists conform to the rules and decisions of the commission whose rulings are final and indisputable.

Austrolebias (Cynolebias) nigripinnis
Austrolebias Cynolebias) nigripinnis

Thus you have order in this aspect of naming all creatures found on this planet of ours. Can you imagine the confusion if every other person discovering a new, or believed new, species went his or her own way? We, as hobbyists, are not bound by the rules or decisions and can call a fish by whatever name we choose but again, what a mess we would finish up in. There would be one fish being called several names by several people, fish being crossed and hybrids being produced. The point of this? Do be very careful to use the correct name for whatever species you handle and so do your bit to ensure that whilst in your hands the species stands a chance to survive pure.

Aquarium Requirements

In the wild a lot of these fishes are territorial by nature, the male defending his area against intrusion by other males. They mate with whichever females they can tempt into their territory but of course some species shoal and will not satisfactorily reproduce unless kept in similar conditions. In the main however, they can be kept in pairs or one male with two or three females. Accordingly they may be kept in relatively small tanks compared with other fish of a similar size. A tank measuring 12" x 8" x 8" will house a pair or trio of killies, in fact up to six of the smaller species can be kept in a tank of this size. Obviously a smaller tank can be used with very good results but from the beginner’s point of view it would be safer to use the larger tank thus lessening the risk of fouling and causing disease.

Aphyosemion sjoestedti Warri
Aphyosemion sjoestedti Warri

As a general guide species of up to two inches will be happy in a tank of the above size, species of up to four inches, in a tank size of 18" x 10" x 10" and the larger species such as Aphyosemion sjoestedti, should be housed in a tank of 24" x 12" x 12". Not everyone will agree with these sizes but if you want good size and good quality fishes (and who doesn’t?) the larger tanks usually produce larger specimens.

Most killies in the wild are found in shallow water so the depth of the tank is not important. A depth of six inches is adequate but a closely fitting lid and I do mean closely, is essential. Killies are excellent jumpers and if you leave a gap in the lid I promise you that they will find it and finish up on the floor! A lot has been talked and written about water conditions for killies. Yes, certainly there are those species that do demand certain conditions and they will not survive or breed unless they are made available to them. However, at this stage of our experience we would do well to avoid such fish as it would be neither fair to the fish or its keeper. You know experience is a great thing and it cannot be bought. It is something learned from life with time and practice, certainly keeping killifish is no exception. In the wild, for the most part, killies are found in soft, slightly acid water. However, experience has shown that they can be kept quite satisfactorily in whatever conditions are provided, within reasonable limits. The most important thing to remember is to acclimatise species to your conditions very gradually. I know only too well that there is always the desire to get a new fish into a tank as soon as possible but this could be the death of them. Not perhaps today or even tomorrow but they could die a few days later all because of a sudden change in water chemistry. This is something that should always be taken into consideration when making water changes with any fish in your care. Do it gradually and prolong its life and your enjoyment of the fish in question. Sudden changes of water conditions can cause gill injury or death due to shock, so please take care. Provided you follow this advice most killies will accept hard alkaline water but I don’t for one minute pretend that all will breed in such conditions. You may well find that you will have to soften and acidify hard alkaline water before some species will breed but again, some species such as the Epiplatys genus, will breed in almost any conditions. So in relation to water make up your mind what you are able to provide and stick to it. Don’t tackle the more difficult species until you have mastered the easier forms. Personally, I have always used aged rainwater to which peat has been added for a short time. A word of warning here, always boil peat before using it, thus removing a lot of the brown stain which leaches into the water in too great a quantity if not boiled. The water, when ready for use, should be tinged slightly brown. In order to prevent disease I also add a teaspoonful of cooking salt per gallon of water. I have always done this and have never suffered any major outbreak of disease

Aphyosemion gardneri nigerianum yellow
Aphyosemion gardneri nigerianum yellow

The question of tank decoration is a matter of individual choice. Killies can be kept in a bare tank with a nylon wool mop as an egg-spawning site. To make a mop take a book of between six to eight inches, wrap around about thirty turns of the nylon/wool, cut at the bottom edge, tie around the folded top and there you have it, a perfectly acceptable spawning mop. The colour? Well I would say stick to colours found in their natural environment, such as brown or greens, but I’m not convinced that it makes an awful lot of difference. If you wish the mop to float then tie a cork or similar object to it. I won’t tell you what to do to make it sink! However, you may prefer to keep your charges in planted tanks, in which case always be careful to select the right plants for the right conditions. Plants needing soft acidic conditions will soon die in alkaline conditions and vice versa. Rachovia brevis blue
Rachovia brevis blue

For years I kept my fishes in bare tanks with either mops or Java moss as a spawning medium but have also kept them in planted tanks which I have come to prefer. I find that most killies breed perfectly well without my interference and will continually produce a stream of youngsters if well fed. They also display better colouring in a more natural environment. However, this is a matter of personal choice as already indicated.
Aphyosemion gardneri Lokoja -wild fish
Aphyosemion gardneri Lokoja -wild fish

When dealing with annuals and semi-annuals the requirements are somewhat different. In the case of annuals only one male per tank will be possible, as males tend to be very aggressive towards each other. They are better kept in a bare tank with just some cover for the females to hide in as males can be very aggressive towards the females and tend to continually ‘drive’ the females to spawn. As they are such hard drivers try to provide at least two females, if not more, to each male. However, do watch them closely for any signs of damage to the female and if so remove her for a rest. As a spawning medium I suggest boiled peat, although it does have the disadvantage of making the eggs difficult to find. Place the peat in a margarine tub, (or butter for those without a ticker problem!) cut a hole in the lid sufficiently large to enable the fish to enter thus helping to keep the peat in the tub. Silver sand can also be used. I’ve tried this but found that it does tend to foul quite quickly and I got the impression that some of the eggs were eaten, they being easier for the fish to find. However, I could be wrong.With semi-annuals either method will usually brings results. They will spawn in either mops or peat fibre or both. So, bare or planted tanks can be used provided that, in the case of planted tanks, the spawning medium can be removed to collect the eggs for ‘dry’ storage (of more later).

PART 2

©Richard Cox 2000 However, any part of this article, excluding photographs, may be used without my permission by any non-commercial, non-profit making organisation anywhere in the world.

 


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