Dicalite Minerals DE25BOX Diatomaceous Earth Pool Filter D.E. 25 LBS All-Natural filtering media for DE swimming pool filters Designed for use in above ground and in ground DE filter systems High-Grade DE filter powder can filter down to 3-5 microns Diatomaceous earth consists of fossilized remains of diatoms, a type of hard-shelled algae Leaves water sparkling and crystal clear without clumping