As for the murky conditions, as long as no chemicals got washed in the mud itself is not a real issue for the fish themselves. Most breeders use actual mud ponds for raising fish. If you have a lot of clay in the dirt compound it is actually suppose to be benificial to the fish, But for the filter it's not so good. As you have read a over flow would be highly recommended. as for what is already in the pond, just simply clean any pre-filters if you have any on a regular basis, Try using batting material, or matala and place it where the water can go through it. Some will place it where the water comes out of the water fall. It can be removed when your showing the pond off or taking pics but will asuure that more particles are removed before the water goes back to the pond. Most should settle out and the pond should be back clear in a short amount of time. If you have a UV light, have it ready to use, The extra nutrients in the water could cause a algae bloom.