PhosGuard is spherical. Its shape allows for maximum water flow through the media. Granular phosphate removers can become compacted, dramatically limiting their capacity to remove phosphate. If the media can’t come into contact with the water, it can’t remove phosphate from it. PhosGuard is the only spherical phosphate remover on the market. ***Aluminum Oxide IS NOT REGENERABLE. No matter what anyone tells you, baking an aluminum oxide media does not restore its capacity to remove phosphate. This misconception comes from the product’s original intended use: industrial air drying. Obviously, if a product absorbs moisture, the best way to remove that moisture is to bake it out. However, that only removes the water, not the contaminants contained in that water.