My pond was red from suspended clay. I limed prior to fertilizing this spring, and poof the water cleared right up. I used eight 50 pound bags of barn lime from Tractor Supply dumped in from shore. $2.99 a bag. It was calcium carbonate, (they also offer a magnesium rich lime).

Sometimes the simple approach works.

4 acre pond 32 ft deep within East Texas (Livingston) timber ranch. Filled (to the top of an almost finished dam) by Hurricane Harvey 9/17. Stocked with FHM, CNBG, RES 10/17. Added 35lbs RSC 3/18. 400 N LMB fingerlings 6/18