I'm building a new Concrete Koi pond approximately 22 feet by 18 feet. Initially we were planning a 5 feet deep pond, but we have hit water table at about 4 feet depth. We are now thinking about four feet deep instead of five feet. We are in Connecticut near Long Island sound and so winters are not super harsh. Pond will have a large volume of over 12,000 gallons.
Any thoughts on how important it is to get to five feet depth for the Koi?