AquaticLife Mixed Bed Deionization Color-Changing DI Resin Filter Cartridge Refill, 1 LiterBrand: Aquatic Life Features: COLOR CHANGING DEIONIZATION RESIN AquaticLife Color Changing Deionization (DI Resin) physically changes colors as it becomes exhausted, removing the guesswork from the consumption and knowing when its time to change it out. REDUCES TOTAL DISSOLVED SOLIDS TO ZERO The mixed bed deionization resin is necessary to reduce Total Dissolved Solids (TDS) to zero in the final stage of an RO DI unit. It uses Cation and Anion to