Anyone how starts keeping kill fish will inevitably loose some fry on the way to rearing the type of specie you have purchased, we all went through it in the begining. I have been keeping killi's off and on for many years and hope this information helps you raise your eggs into full size killi's more successfully.
When your eggs arrive, resist the temptation to rush about opening and wetting your new acquisition. there is usually plenty of time. Depending on the type you have chosen, they will arrive either in a zip bag with peat or in a bag/file/transit holder, with a tiny peice of plant material. The eggs should be eyed up, that is, you should be able to see the tiny eyes within the egg, this indicates that the eggs are in fact fertile. take a container and add a small amount of aged tank water. (about 1" deep is more than enough).
If the eggs are in a file or come attached to a small mop, place the eggs and what every they were sent with into the container, now this is optional, but I always add one drop of Metherlan Blue to the water, this prevents fungal attack during the remaining time they take to hatch. Place the container in a dim light area and maintain a steady temperature of 20c to 23c this temperature range is due to the fact that some killi's fare best at 20c and others like 23c. ask the supplier what he keeps his fish at to know the temperature required. Observe the eggs and as they hatch out, remove them very carefully with a pipet to a growing container, this needs to be three times bigger than the hatching container, as a guide it should have appoximatley 12 sq inches of surface area, infact the more the merrier. but keep the depth to about the same as for the hatching container i.e. 1".
Once the fish are swimming around you will need to start feeding them as they have now absorbed their yoke sack. use infusoria, micro worm or newly hatched brine shrimp. (caution) make sure there are no brine shrimp egg cases in the tank when you feed with this type of food, it can kill your fry as quick as a wink if they try to eat them. Killi's will grow at an alarming rate so they need constant food to maintain health. change the water in the rearing container at least every day to start with, once they are big enough they can be moved into a small tank and the depth increased gradually until the tank is 3/4 full. Last thing to remember killi's jump, if you don't want to find them on the floor in the morning keep a tight lid on them at all times, if there are wires or airline pipes going into the tank, put some filter wool round the hole. for filtration I use a sponge filter, as these are far the best for killi's but a box filter would do, if you don't have one.
I wish you every success with your new fish. Killi's are well worth all the effort and will brighten up your community tank no end.......enjoy.