Expanding on its line of reverse osmosis (RO) and deionization (DI) water filtration systems, Aquatic Life introduced its Twist-In (TI) RO/DI Systems to the aquarium marketplace. Available in three-stage and four-stage units, the new models feature twist-in cartridges with pivoting heads for fast and easy replacement of filter media. Using carbon and sediment cartridges with a central membrane, the TI 3-Stage RO System removes harmful substances such as heavy metal ions and totally dissolved solids from tap water. The TI 4-Stage RO/DI System takes water purification one step further, utilizing a fourth cartridge filled with a high quality mix bed color changing resin. As the filtered resin absorbs the impurities, it changes colors to notify users when to replace the resin media.