Simply Koi and More Koi

Dear All, Hello, Just joined so finding my way around! I am absolute beginner but am in the process of designing my first pond 6000 Gallons, 1.2 meters below ground and 0.7 meters above total depth 1.9 meters, block work walls, welded box liner, Gravity system with 2 aerated bottom drains, 2 DIY fil...