Schmidt, I'm late to this discussion and new to the forum. Years ago I read the same article referenced earlier and decided to try gypsum purchased locally (Lowe's). Long story short: I knew each pond would be unique in its requirements so I charted a gypsum vs. visibility chart (attached). I would dose gypsum, wait a few days and measure visibility. The lower curve is the first dosage; the pond turned over and I started dosing again and as you can see the curves were the same but picked up quicker the second time around with the higher curve. Knowing the curve for your pond will allow you to know how much gypsum to achieve how much visibility. If gypsum doesn't work try Applied Polymer Systems/Atlanta, GA--they have some good solutions if you can accomodate the required systems, which I have had a hard time doing. FYI our pond is small (.35 acres/6 ft deep).
