Deep water and volume:
The depth, There shouldn't be any shelves, the reason I say that is to keep out un-wanted predators that will be able to wade into the pond and steal your fish like Blue Heron or Raccoons. So make sure the sides of the pond are straight down as possible and not sloped. We want deep water, the deeper the better. Koi exercise more swimming up and down and will have better circulation systems and body conformation. Keep the stones and rocks out of the pond; they are using up valuable volume for water. Stones and rocks make cleaning imposable unless you remove them each cleaning. Parasites and hydrogen sulfite find a home on, in and under these surfaces; use them out side the pond. Plants are better used out of the pond for the same reasons, they use more then they give. Plants have no place in a koi pond. It’s all about the Koi; they are the beauty in the water, ”They Are Your Pond Jewels”.