PhosGuard rapidly removes phosphate and silicate from marine and freshwater aquaria. It is not recommended for phosphate buffered freshwater. PhosGuard is highly porous for high capacity and bead-shaped for optimum water flow. It outperforms all competing products. 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 cant come into contact with the water, it cant 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 products 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.