Added 40 granite cobbles to the edge of the pond over the weekend. Purchased them for around $1.49/ea from Menards. The goal here isn't to cover the entire surface of the tarp; just that which is above the water line. Granite gives it a nice, natural look, and provides less surface area for evaporation and algae growth than sand, dirt, or river rock (algae has not been a problem yet this year; not sure if that can be chalked up to the fish, the snails, the added plants, the excavating we did in the stream, or sheer luck).

The stones also provide a hiding and hibernation spot for frogs and other amphibians, most notably the Spring Peeper, who will overwinter above ground, basically freezing in place between stones or rocks or in logs, only to return to life the following spring.