How do I introduce my new fish to my pond?
  After transporting Koi, float the bag (unopened) in the water for about 30 to 45 minutes to allow the water temperature inside and outside the bag to equalize before releasing the Koi. Koi can withstand a wide range of temperatures, however sudden changes in temperatures are not good for them. When introducing new Koi to your pond, be careful that they don't jump out, especially near the waterfall. Remember that stress is a major cause of Koi deaths. Stress may result from changes in pond conditions, over handling, over medication, etc.