DIY 3-Barrel Filter System for Koi Pond - Adding Media and Starting Up

4500 GPH pump did not work as I originally planed. So switching to JEBAO DCT 12000: 3170 GPH pump works well for this system K1 media: https://www.fishfarmsupply.ca/ K2 media: eBay.ca (www.Onlineponds.com) Most plumbing fittings and pipes are ABS as ABS costs less than PVC.