Removes phosphate and silicate. Phosphate is a byproduct of fish metabolism. Silicate is added to tap water to reduce pipe corrosion. If left to accumulate, these chemicals will lead to reduced water quality. Special Filtration Material That Selectively Removes Phosphate And Silicate, Common Nutirents Found In Fresh And Saltwater Aquariums. Chemical Filtration Mechanism. Use One 150 Gram Pouch For Every 55 U. S. Gallons.