hw-ionic® is a special filter medium for freshwater and seawater aquariums specifically developed to securely bind ammonium and nitrite, the preliminary stages of toxic nitrate. A unique combination of special activated charcoal and selected ion-binding resins capture the harmful substances securely using a negative pressure of 100 bar and does not release them back to the water even if the filter medium is supersaturated with toxins and pollutants. Dreaded and highly toxic nitrate can therefore not be created in the first place.