What is the ideal depth for a koi pond?
A In my experience of over 25 years, 4 to 5 feet is ideal. You need a minimum of 3 feet for koi fish for several reasons. Safety for fish from wading cranes they can not wade in 3 feet of water. Plus the water temperature in shallow ponds fluctuates too much with the changes in ambient temperature. The greater the volume of water, the longer it takes for the temperature to change. Warm water or fluctuating temperatures are unhealthy for fish.