Thinking about adding to your koi population? Then consider koi fish breeding. The pastime can vary from a hobby to a full-out profession. If you have the time, space, and budget to expand your koi collection, koi breeding may be for you! Koi breeding is an easy way to expand your pond’s population and can earn you quite a bit of money. Sometimes in larger sized ponds koi fish will reproduce on their own. In most cases, if you’d like to add to your koi populations, steps need to be taken to formally breed.