Cecil, have you tried that method succesfully? I cut plastic barrel in half, and filled both parts about 6" deep with pea gravel. My water is chocolate color, so I can't see what is happening. But after couple of years I pulled them out and they look unused (no nest shaped depressions). I wonder if the high edges had something to do with it. Now I sank 12'x12' tarp to keep the gravel from sinking into the mud and am in the process of creating 4" deep layer of pea gravel on top.
