I would be very curious to get the soil tested just under the muck line. I have seen a few folks on here who have renovated a pond like this but had problems with clarity and algae blooms after it filled back up. I am wondering if a high degree of nutrients leaches out of the muck into the subsoil being exposed, and if so, how to remedy that nutrient load so it doesn't return to the water too fast. Now would be the opportunity to check it out.
If high in nutrients, perhaps line the pond with a fresh layer of clay before filling? Perhaps dig a little lower and see if there is less down below?
You were right on the nutrients being a problem. I ended up having to leave one corner of the muck so there were more nutrients left behind than I wanted. But mother nature decided it was time for the fall rains to come and that muck had to stay where it was.
The first year was not much of a problem. But the second year my son did have a lot of FA problem from excessive nutrients. I think this year he is trying to keep that contained but have not heard from him how he is getting along with it.
His kids are in the pond almost daily during the summer. Either swimming, kayaking, rubber boating, fishing, etc. They get a lot of use out of it.
