I helped my old pond, which was turbid from suspended clay, by adding some ag lime and later adding some rock lining along the shore lines that were subject to wave action from wind.
Those two things helped considerably. As I understand it, ag lime can help with some clays but for others alum is needed. I have no experience with alum.
Then it seems like the pond naturally got clearer as it aged.
Oh, the other thing is we had a number of BH catfish early on. Now the LMB have mostly cleaned them out as we hardly ever catch one. I think they kept it turbid while they were in there in numbers.
