The Reef Octopus Direct Current (DC) pinwheel skimmer pumps offer the latest in variable speed flow technology, providing precise control, improved efficiency, and superior performance. Unlike most hobbyist skimmer pumps that use Alternating Current (AC) power, the DC pumps allow for greater control over motor speed and, in turn, the air and water flow rates into the skimmer. Plus, with the advanced VarioS Controller, users can take advantage of added features such as a float switch connection for added security, pause/feed modes, and compatibility with third-party controllers for even more intricate control. The VarioS 4S Controllable Skimmer Pump also features a slow startup ramp and a detachable waterproof controller for ease of use. Please note that some models may require an additional part for conversion, which must be requested at the time of purchase.