I have pond that holds about 15,000 gallons of water. It has cvreated a leak that I can not find. It is down to about a foot and and the leak has slowed down. I have checked along the seam and can not find anything. I also tried the oatmeal idea, where you spread some along the top of the water and watch to seei if it floats down to the hole. No luck. I don't want to drain the whole pond if I don't have to as I have some koi in the pond and did not wat to disturb them. Any ideas??? Thanks.