Temperature Koi
Generally speaking Koi should not be subject to more than a 3 - 5ºC sudden change in water temperature. Always adjust the temperature gradually when moving Koi around. An increase in temperature is tolerated better than a decrease in temperature. Most ponds have a 1 - 3ºC variation in temperature in 24 hour cycle. You will notice that Koi are more affected by a sudden lowering of water temperature than a sudden raising of water temperature.