Killifish are different than most other Aquarium fish in that the females lay a few eggs every day, as opposed to a lot of eggs at one time. Therefore you usually allow them to remain in the spawning tank for about 2 weeks before you collect the eggs.
Soil Spawning Killifish are unique in their spawning methods. In the wild these fish live in temporary pools of water that form in the wet, or rainy, seasons of Africa and South America. When the wet season is over the pools dry up. The way these fish survive this is to grow quickly and lay eggs in the mud while the water is still available. When the dry season comes the pools completely dry up but the eggs remain viable deep in the mud until the return of the wet season. Then the eggs hatch and the whole process begins again. These fish have miraculously adapted to this lifesyle and thus the species have survived.
The Cynolebias Alexanderi is an excellent example of a soil spawning killifish
The typical spawning set-up for soil spawning Killifish would be a 2 gallon drum bowl, good clean water, well fed and conditioned breeders, and some peat moss. The best peat moss would probably be the peat pellets you can find at most Garden Centers. If not then you can use regular peat moss that comes in large bales, but it will need to be boiled before using it, to kill any microorganisms that might be present and to make it sink more readily. A variation of this spawning method would be the use of a larger tank such as a 10 gallon tank, in which you place a smaller vessel to hold the peat material (example above). Don't worry the breeders will usually find the peat,wherever it is placed.
Once the spawning tank is set up, you add the breeders. Usually it is best to have 2 females for 1 male. The males tend to be treat the females pretty rough if only 1 female is present. And it's always best to use only one male at a time so that he will spend more time spawning instead of sparring with a rival.
It's best to feed the breeders only live food if possible while they are in the spawning tank. Old rotting food will contaminate the eggs very quickly. If no live food is available then feed very sparingly.
After about 2 weeks you can collect the eggs. The eggs will be buried and hidden in the peat moss so it's always a guess as to how many eggs are actually there. Just collect all the peat moss with a fine meshed net. Gently squeeze most of the water out and place the ball of peat on a paper towel for further drying. It should end up moist but not dripping wet. After its dried to your satisfaction place the peat ball into a plastic sandwich bag or something similar for storage.
The incubation times vary from about 2 weeks to 6 months. You'll have to find out what the incubation period for your particular species is, but a good compromise for most species would be 10 weeks.
When the time comes to try to hatch the eggs just put the peat moss in a shallow pan and add no more than about 2 inches (10 cm) of water. Most eggs will hatch within 24 hours. The fry can be scooped out with a spoon, or caught with a eye dropper, and transferred to a rearing tank.
Nearly all Killifish fry can accept baby brine shrimp as a first food. Micro worms can also be used. They should receive only live foods for the first month or so and then can be weaned over to flakes and frozen fare if necessary.