Hey cimdma,
Welcome! Good to see another Louisiana guy on the forum.
Your problem is most likely soft rain water caused by all the rain we have been getting for the past year or 2. Your pond water is probably flushed out and replaced by soft rain water, which holds fine clay in suspension. Rain water is usually a bit on the acidic side, so you may want to do a PH test before adding magnesium sulphate, which is also acidic. It may be more appropriate to add a base to clear it, such as gypsum or hydrated lime. Gypsum is mild and harmless, but watch out for hydrated lime, which needs to be applied carefully. No need to totally clear your water while the pond is brimming full. Get it partially cleared while full, and when the level drops a foot or so in the dry season it will finish clearing.
