A special filtration material that selectively removes phosphate which clouds the water. Phosphate is released by fish waste, decaying organic matter and tap water sources. Also removes silicate, a natural mineral found in tap water. Keeps water clear and tanks clean. Does not remove trace elements and does not affect pH. * Safe for all fish, invertebrates and plants. * Promotes growth of reef-building corals by preventing calcium and magnesium precipitation. * Use in fresh, saltwater and reef aquariums. Treats up to 208L 1 Large Pouch.