Hello, I am very new to pond keeping. I have a circular pond that is about 15 feet in diameter. The pond is along side a small stream that is about 5 feet wide, and moves fast enough to move water in the pond, but slow enough for a small fish to not get caught in the current. I think that the pond is natural, but if it isn't, it is at least 20 years old. I would like to keep KOI fish in the pond. (Remember, I am very new and and information helps) . The pond is about 3.5-5 feet deep. I would like to know what matenance would be required, and any tips on adding/stocking/feeding/breeding KOI fish would be Very helpful. Thank you.