I had excellent results from adding gypsum. I purchase it in 50lb bags from my local farm fertilizer store $3 a bag.
Its pelletized, I mix half a 5 gallon bucket with water to make a slurry, then toss it into the water.
The gypsum acts as a colloidal. I add it in the spring. It clears up the suspended clay in about 2 weeks.
Most of my turbidity comes from my inlet.
This is a pic I took after a rain. It tells the tale. My pond is 100% clay.
