Water temperature in the pond varies from region to region. Nonetheless, for all regions one can expect the water temperature to go down starting in mid-September. Coinciding with this time of the year and drop in water temperature, Beni starts to increase its intensity. A large Koi is not known to develop well simply by the continued practice of usual feeding methods from winter to early spring.

What is most remarkable is that even if a large Koi is kept in a heated pond during the winter time, and then transferred to a mud pond to spend the spring and summer months, at the harvest time in autumn, the effect of such pampering on the fish will not be particularly impressive. The change of seasons, the natural environment, are all responsible for the development of a healthy and beautiful fish.

The natural environment with its seasonal changes, especially the cold winter, develops toughness and natural survival instinct in the Nihsiki Koi. These experiences will elicit habits of eating in the summer to store energy and strength to survive through the winter months. Moreover, it learns to develop the appropriate body mass for its age, again, in preparation for the winter. A critical point here to remember is, when the water temperature is low, it is best to provide food with reduced protein content and the total quantity restricted. We will talk more about it in the future.

Animals that hibernate instinctively know how to prepare for the winter and store energy to survive. They are all occupied to consume food in the summer to store enough reserves to survive the winter. A proper winter experience for the large Koi is very important for its development. For a cold-blooded animal such as the Koi, water temperature is of particular importance. The Nishiki Koi must sleep or less active in the winter. This is determined by nature. To go against it, and keep the fish in a very warm pond in the winter, will upset its bodily functions and balance.

The overprotected Koi is certain to disappoint the hobbyist in the fall harvest. If resourceful enough, one could experiment to see the differences between a Koi that experienced cold winter and a koi that did not. Even if these two differently cared fish are kept in the same mud pond over the summer and then their development compared at the harvest time in the fall, results will be as explained above.

In terms of Tosai, however, it does not have eggs and it is good to keep them in warm water and develop its size quickly. By doing so, one can see its potential quickly. Good Koi becomes beautiful and becomes very attractive quickly.