Robelle diatomaceous earth powder is an all-natural, porous powder derived from the tiny fossilized exoskeletons of algae-like water plants known as diatoms. When used in D.E. filter systems, diatomaceous earth powder provides a remarkable filtration media, trapping debris and contaminant particles ranging from leaves and dirt to bacteria and other microorganisms. Fresh diatomaceous earth powder is required every time you backwash your D.E. filter and will keep your filter working at peak performance. Robelle D.E. filter powder is of the highest quality and will provide you with outstanding filtration results that will leave your pool water sparkling clean.