Regenerative, alkaline anion exchanger with high silicate selectivity. Binds residual silicates in the permeate (pure water in the reverse osmosis system). 1,000 ml binds up to 10,000 mg of silicate. Especially silicic acid concentrations in tap water often pose a problem in aquaria in spite of using reverse osmosis water. With of a silicic acid concentration of 5 mg in the tap water and a reverse osmosis system´s retention rate of 95 %, the remaining silicic acid concentration in the permeate is still 0.25 mg. Even this concentration may cause a silica algae problem.