Captive Purity represents the highest quality in reverse osmosis technology. Captive Purity Reverse Osmosis Systems meet stringent standards and far exceeds the quality of systems from other manufacturers. A wide variety of options ranging from economy 2-stage units to top of the line 4-stage RO/DI units are available to suit your exact needs. Drinking water systems and custom installation solutions are available. Captive Purity Reverse Osmosis Systems are engineered and manufactured under strict guidelines to produce extremely pure water with exceptional focus on minimizing phosphates and silicates. This is a very important feature for reef aquariums.