On the question of temperature, killies prefer a much lower range than the average tropicals. In fact if they are kept at too high a temperature they will soon let you know that they do not like it. Aim for a temperature of between 20º and 24ºC. (68º and 74ºF.). Only in a few species does it require a higher or lower temperature to be used.
In the wild killies eat mainly terrestrial insects, aquatic insects larvae and crustaceans. Accordingly, they do better on live foods but most will eat dry foods provided they are supplemented by live foods or high protein food such as minced beef heart. Favourites with killie keepers are Grindal worms, white worms and tubifex worms – although I personally do not recommend tubifex worms as I feel that they tend to foul small tanks quickly – wingless fruit flies, Daphnia, Cyclops and bloodworms. The latter are particularly good and are eaten with gusto by most killies. Good quality flake food can be given but do so sparingly. Remember you are usually feeding only a pair or trio of fish as opposed to the usual tank full! Many other foods can be used and are readily taken. In respect of other foods it is a question of suck it and see. If anything given is uneaten then do remove it to prevent fouling the water. This of course is applicable to all foods given; never leave uneaten food for any length of time.
Non annual species can be dealt with in two ways. Firstly they can be left well alone in a well planted tank and, provided cover is available for fry, they will usually come to no harm left with the parent fish. Secondly, the eggs are
collected from the spawning mops and incubated in small containers. Most hatch between 10 and 30 days after spawning depending on the temperature at which they are kept. The lower the temperature the longer will be the hatching period and vice versa.
On hatching very small fry will need infusoria as a first food. These are the small microscopic animals occurring naturally in water. A culture can be made using something like a bruised lettuce leaf in a jar of aquarium water. After a few days the tiny creatures will be seen with the aid of a hand magnifier and can be poured into the hatching container. Most fry will readily take newly hatch brine shrimp nauplii but do be careful with these as they soon die if uneaten and will very quickly foul the container and your fry will die. Most killie keepers use 500gm size margarine tubs as hatching containers so you can see that it will not take much to foul these. If too large a container is used the fry will find it difficult to locate their food and will thus starve and die. In most species growth is moderately slow but sure and a lot will live for three to five years. As they increase in size move them on to larger containers until by the time they are about half an inch long they can be transferred to an 18" tank.
With semi-annuals I find the best method is to collect the eggs. Don’t worry about handling them as they can withstand considerable pressure. If they break when you pick them up then they were infertile anyway. Store the eggs on moist peat at the required temperature. By moist I mean more wet than that described for annuals. Add water to the peat until it can be seen just under the surface between the particles but not sopping wet if you understand. Just place the eggs on this so that you can watch their development with a hand magnifier.
The fry inside the egg will usually let you now when they are ready to hatch. As a general rule when you can clearly see the fry’s eye, fully formed, it is ready to hatch. Return the eggs to water and they should hatch between four to ten hours. More often than not some will hatch within minutes of being returned to water. Others may not hatch and will require to be re-stored for a further period. Some of the semi-annual species can be very difficult to induce to hatch. Although the eye can be clearly seen and the fry look fully developed, the egg just sits in the water looking back at you! I remember a strain of Fundulopanchax amieti that positively refused to hatch no matter what I did. I never did solve the puzzle of what I had to do to breed this one! Feeding semi-annual fry is much the same as non annuals. Usually the fry are much larger and take brine shrimp nauplii and microworms followed quite quickly by Grindal worms as a first food. The fry grow quite quickly so the food requirements are that much more. Only experience will show you how much to give.The eggs of most annual species have to be stored in ‘dry’ peat for anything from six weeks to nine months depending on the species involved. Now what do we mean by ‘dry’? Well by dry I mean damp. Aim for the same dampness as newly opened tobacco. Remove the peat from the spawning container using a very fine mesh net to hold it. Gently squeeze out all the surplus water. You will not harm the eggs; they can withstand tremendous pressure when you consider some are as small as a pinhead.
When all the surplus water has been removed place the peat and eggs into a plastic bag and mark it with the date and species name. Then store the bag for the appropriate period at a temperature of about 25º to 26ºC (77º to 79ºF.).
A high shelf in a fish house or an airing cupboard will be suitable. On returning the eggs to water, having ascertained that they are ready to hatch by checking the eggs for the fry’s eyes, be sure to add salt to the water. A lot of annuals are prone to velvet disease and this will help to prevent it. This disease manifests itself as very fine peppery white specks on the side of the fish and with fry you just do not see it. Some very small annual fry will require infusoria but most will take brine shrimps immediately. They eat well and grow at a fantastic rate. With annual species you must pay very particular to the hatching container. It must be kept clean at all times and any uneaten food should be removed. It is also advisable to put a couple of small aquatic snails in the hatching container.
Just a word here about the phenomenon known as diapause. This is a natural device, which triggers or inhibits the growth of the embryo within the eggs of annual species. In any batch of eggs there will always be some ready to hatch whilst others have only developed to resting stages. So having returned the eggs to water, after you are satisfied that there are no more fry hatching, re-dry the peat and re-store for a further period, usually another month. Re-wetting can then be tried. I have known fry to hatch after each of four separate wettings. This is nature’s way of ensuring the survival of the species should the first rains fail and the pool dry after the fry have hatched. Thus, even though rains may fail completely for a season or two, viable eggs will still be in the mud at the bottom of the pond.
There is nothing mysterious about killifish, they are no more difficult to keep and breed than any other tropical species. The average aquatic dealer cannot obtain stocks and when they do the price is usually high. However, within the British Killifish Association there are usually a hundred plus species available and details of how to find us are within this web site.
Well there you have it. I have tried to give a full as possible general introduction to killie keeping. I sincerely hope that some of you will venture into the world of killies and enjoy this aspect of fish keeping.
©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.