Pond depth – The depth of the pond is also very important. A koi pond needs to be a minimum of 3″ deep. Any shallower than that and you will be constantly loosing your koi to predictors such as blue herons or raccoons. Even if only one area of the pond is shallower than 2″ you will probably need to net the pond to keep your koi from getting eaten. Now if you are looking to grow large koi you will need to go down to 5″ or ideally 6″ deep. At this depth, the pressure from the water compresses the koi’s body. The constant compressing of their body near the pond bottom and then the relaxing of the pressure as the koi swims toward the surface helps keep their body shape firm. Large koi that are raised in shallow ponds tend to develop an irregular body contour. Additionally, deep ponds hold their temperature better. Constant temperature swings can be stressful to koi. Deep ponds will be cooler in the summer and warmer in the winter.