Typically, this means 12 to 18 inches lower for the mesh covers, 3-6 inches for the solid floating covers. This variety keeps debris from entering normal water and retains the heat from day time keeping the actual warm on cooler a short time. If planted at the edge of a pond, it will reach into the water like rays of sunlight. The sand bed may be clogged with mineral deposits that will not backwash away on vacation.