The Water Wych is a revolutionary new way to keep ponds clear and greatly reduce algae problems. Algae grows off of minerals and nutrients found in pond water. The Water Wych is a natural blend of volcanic rocks, carbons and silicates that absorb large amounts of nutrients and minerals from the water thereby greatly reducing the available "food" that algae needs to thrive. The Water Wych is a self-contained filter that simply sits submerged in the pond, for best results place in an area of flowing water. Once the organic materials in the Water Wych have absorbed all the minerals and nutrients they can, they can be used as fertilizer. Typically the Water Wych will need replacing every six to nine months. Water Wych is 100% organic - no chemicals! The Water Wych is available in four sizes for you to choose from, depending on the size of your water garden.