How do you fertilize koi eggs?

To fertilize koi eggs, the male koi must gently nudge and chase the female as she lays her eggs, typically on spawning surfaces like plants or spawning mats. During this process, the male releases sperm over the eggs to fertilize them. It's important to ensure that the water conditions are optimal, with appropriate temperature and cleanliness, to promote successful fertilization and development of the eggs. After spawning, it's advisable to remove the adults to prevent them from eating the eggs.