I live in northern Ohio just installed our new pond this past weekend. It is 6 foot by 4 foot by 2 feet deep. We currently have 6 goldfish and one Koi. Yes we do know eventually the Koi will have to be removed into a larger pond, which we hope to build next summer. Our pond has a lot of natural elements such as plants, river rock coating the bottom and some natural field rock that we have made into little "caves" for their protection. We also made our own biosystem and so far the water is crystal clear.