It's not real muddy at present, you can see down 18" or so, an opaque gray-brown color.
You're lucky then. You can use gypsum as Ryan said. I takes literally tons of gypsum to clear up a real muddy pond, but it it's not very muddy, a few sacks of gupsum may finish the job.
Dollars to donuts your water is more likely to be acidic than base, so gypsum is perfect... very easy on existing fish.
