My backyard pond turned green enough that I could barely see the fish. Here is the exact pump, 36W UV clarifier, DIY 5-gallon filter, 20-PPI foam, lava rock, bypass plumbing, mistakes, and before/after results from my real 1,200-gallon pond.
My 1,200-gallon pond uses an 1,800 GPH pump, UV clarifier, filter, bypass, and waterfall. Here is how I chose pump size and why rated GPH is only the starting point.