15 cm koi eat S-size feed. This kind of fish is a common ornamental fish, which belongs to wide-temperature fish. It does not require high temperature and can survive in the environment of 5-30 ℃. Its own eating habits are miscellaneous, and there are many things to eat. If it is artificially raised, it is best to pay attention to the collocation and replacement of feed to ensure the balance of nutrition. Usually, it should be fed three times a day. After each feeding, it is best to finish it within 5 minutes.

1. Food selection: If you want koi fish to grow fast, you should feed more water earthworms, shrimps, red worms and other foods. This kind of food has high protein content and comprehensive nutrition, and koi fish grows faster after eating it.

2. Control food intake: Koi is an omnivorous fish with a wide range of foods, and it is open to many foods. Water earthworms, red worms and other foods must not be fed too much, because it is easy to support koi fish and increase the burden on their digestive system. The amount of food fed must be moderate, and it is best to keep koi fish full at seven points.

3. Change and match: It is best to change food frequently, and do not feed the same food for a long time, so that the nutrition of koi can be more comprehensive. Changing food can also keep koi fresh and avoid anorexia.