You can purchase bulk gypsum at the Temple-Inland Fredericksburg Quarry. They are located just north of Fredericksberg Texas. Their phone number is 877-585-5896. I purchased 6440# yesterday. It cost $90.38. I haul the gypsum in a dump trailer, it must be tarped. You can also purchase gypsum rock. The size about basketball to 3X basketball. I plan to put some of the rock in the shallows where the wave action can work on it. This should give long term results. Hope someone can use this info.