Keep your aquarium free of phosphate and silicate with API's Phos-Zorb Pouch. Phosphate, which is found in fish waste, tap water and decaying organic matter, can make your tank cloudy. When silicate starts to build up in your aquarium, it can create patches of unsightly brown algae. The Phos-Zorb Pouch is scientifically proven to remove both compounds from your tank, resulting in crystal-clear water.