If you want to breed Koi, there is lots of basic information that you need to know and understand in order to get started.  Here i’ll just give you the basics but it will provide a structure for you to follow:

 Select healthy Koi of the variety you want to breed.  Make sure that they are suitable and of high quality to make sure that they will spawn good quality offspringRemember that the ideal months to start breeding is between April and July.

Breeding Koi should be about 25 cm (10in) in length to ensure that they are sexually mature. The ideal Koi male for breeding should be 3 to 5 years old, while a 4 to 6 year old female is best, being at its prime. 

Specimens chosen for breeding need to be conditioned for a year.  The best combination is two males to one female, a “ménage a trois”.  You need to put them in a separate “spawn pond” or tank to ensure genetics. 

Setting up the location. There are several things that the fish needs in order to breed.  The following needs to be ready and in place as soon as the Koi are ready to spawn.
•    Koi aquatic weed habitat or medium or place where they can lay their eggs. Artificial medium can be used if water plants are unavailable;
•    Privacy – the newly hatched fry, being unable to swim yet, need a safe and secure place where they can hide;
•    Top quality water and correct pond temperature

Eggs:  You need to separate the eggs from the parents because they can be eaten.  After spawning, and after the Koi have been removed, treat the pond with malachite green to prevent fungus from forming on any infertile eggs. Maintain the temperature at 23oC and wait a couple of days for the fry to hatch.

Hatching:  After hatching, let the fry pass without feeding for 3 to 4 days.  Afterwards, bring them a very good source of abundant food.  Seventy to 75 degrees is the ideal temperature for growing fry.

Feeding fry: Take note that they still do not have any developed taste buds, so they can only detect food by sight alone; thus, they need to have food all around them.  For the first day or so, hardboiled egg yolk is the ideal food. Another good food source is brine shrimp, especially when the fry are about a week old.  After that, you can start feeding them a mash diet. At the end of the week, you can feed the Koi of a size that can be eaten by the smallest Koi in the pond.