Keith, No, never considered putting koi or goldfish in it. It's full of old trees and logs in the deep end. (18 feet deep) That's whey we could only seine the one side. I am trying to make every attempt to keep all exotics out of that pond. that for the kids and all to fish in and enjoy. In the back I started working on one of the Mud ponds for Koi fry and water plants but had a delay and it filled up with water. Never has dried out for me to get the tractor back in it. For now it's a glorified Tadpole nusery. I know it has at least four kinds of frog taddies in it! LOL Guess I'll save that and the lined water lily pond for later this fall or next year. I am considering heavily on some small breeding, thinking more toward goldfish than koi, But the first year or two, I'll just take what breeds and raise. To get practice and kind of work through the unknowns........ :yikesu: