When do they breed and will they eat their babies do they have to be a certain age before they breed or special type of water i have a pond and have no babies of koi yet?

Spawnings in koi ponds will occur spontaneously, provided sexually mature males and felames are present, water temp and light levels have been high and long enough "degree days", and there is a medium within which eggs can be laid and fertilized. However, many spawnings go unnoticed, because the parent koi immediately devour the eggs. Except in heavily planted ponds, any stray, free-swimming fry will soon be picked off. You would have to intervene before the eggs hatch, separating them and then providing spacious accomodation and limitless live food as soon as the fry are able to eat.

Answerthe above answer is true but also spawning can be induced with a water change of 30% or after a heavy down pour....