Phosphates enter the aquarium primarily through tap water additions for evaporation or water changes, food addition, particularly brine shrimp, some other frozen foods and use of inexpensive carbon. Silicates enter the aquarium primarily through tap water (natural water contains silicates and water companies add sodium silicate to control equipment corrosion), poor salt mixes, and also improperly filtered additives made from tap water. Phosphates and silicates should be first controlled by the use of water made by reverse osmosis or deionization, limiting phosphate bearing foods and use of a good grade of aquarium carbon from a company you trust. Reef-Basis - Captiv Phos Fe should then be employed to reduce the phosphates that remain, to a level of .04 mg/l (ppm) or less.