Help clear up unsightly cloudy water caused by phosphate and reduce aquarium maintenance with API Phos-Zorb Filter. Phosphate can come from tap water, fish waste, uneaten food or dead algae. In freshwater tanks, high phosphate levels can cloud water and dirty aquarium glass and gravel, increasing the need for maintenance. API Phos-Zorb Filter removes phosphate and silicate for clearer, cleaner conditions. It also removes compounds that prevent healthy plant growth and promotes the growth of hard and soft corals in saltwater tanks. API Phos-Zorb Filter comes in a convenient pouch. Just place it in the water flow of the aquarium filter and replace every two months or when there are high levels of phosphate and silicate.