Last weekend I finished converting our 15' above-ground pool into a grow-out pond for some of our precious Koi. With over 5,000 gallons of swim area, it should do nicely. I used a single 7,000GPH external pump, which was my first time using an external pump since I used submersible pumps for each of our earlier ponds. So far, so good. It's extremely quiet and seems to be doing the job. As always, my filter setup is completely DIY. I used a total of five 55-gallon plastic barrels to build my upflow filters and commercial pond filter pads as my prefered filter media. I used 2" PVC and 4" ABS for all plumbing, and I added a total of five bottom drains...