Brent, After my pond filled up I sank wood pallets. I tied bundles of 5 or 6 together with nylon rope and attached a concrete block to it. Then I towed the pallets to the location desired, and anchored then with a few bricks and string. The pallets will not sink until they become waterlogged, a week or two in my case. In my 3.5 acre pond I sank 15 bundles.
