A unique four way action pond pad which can be used to clear pond Algae in all situations. Algae Pads works four times better than Barley Straw and clears most ponds in four days. Algae Pad offers environmental, biological, chemical and mechanical control on over 80% of all known Algae species. Can be used directly in the pond or preferably in external biological box filters. The algae pad comes in one size and is very easy to use.