A: Great question! There are many facets to this questions and also please note that a pond will never be as clear as a pool. If your pond is murky, the first question I would ask you is, "Do you have catfish or koi in your pond & lake?" If the answer is "yes", then thats the issue. Catfish and koi are known as "bottom dwellers" and will stir up the bottom of a pond and no matter how hard you try to settle it out, the catfish and koi will just keep stiring it up. If you do not have catfish or koi, then we have to dig a little deeper for find the answer.
What I would do next is a glass jar test. Take a clear glass jar and fill it up with your pond's water. Wait 24 hours and either two things will happen. One, the cloudiness settles and the water becomes clear or two, the water is green and nothing settles. If the water is green, than we have to treat for algae. See Algae Control.
If the cloudiness settles at the bottom and the water is clear, then the cloudiness is caused by suspended particulates instead of algae. If this is the case, a double dose of Nutri-Defense will flocculate the particulates and a regular maintenance of Pond-Clear Packets will help maintain that clear water. Also, Nutri-Defense & Pond Clear are both safe for people, pets, fish, livestock & wildlife.