Our Koi pond was quite a challenge….on that same spot we found old two septic tanks and had to dig them out…well at least we dug out one…the other one was made out of concrete so we left it in and dug around it…made a nice ledge for my water lilies. We're the proud owners of 37 Koi, the babies they had in Washington are still alive…well all but three of the 17 babies we brought with us survived