bowtiebubba,
If your mind is set on gypsum, then simply disregard my response....but if not read on:
Ag. lime is readily available in almost all farming areas, is relatively inexpensive, is long lasting, is very effective, and not the least of factors, is easy to apply. I've had great results with it for many years in ponds.
The method I use is first, get a water/soil test to determine how much is needed. Order the ag. lime from a local co-op, feed store, or fertilizer dealer. They will also have the large spreader trucks needed to apply the lime. Then have the trucks back up to the ponds in several places and let it fly. Also apply in the direct drainage areas for your ponds. In my area this spring/early summer I purchased the ag. lime for $35 per ton spread price. I generally use about 4 tons per acre in a new pond and it lasts many, many years.
