A New Benchmark Protein Skimmer Performance and Control The Reef Octopus controllable Direct Current “DC” pinwheel skimmer pumps are the latest in variable speed flow technology and allows for refined control, enhanced performance and efficiency. The vast majority of skimmer pumps available to hobbyist are alternating current "AC" pumps (the type of power that comes out of your wall outlet). Direct current pumps have several key advantages over traditional AC pumps. Most notably, you can control the rotational speed of the motor, thus electronically control air and water flow rates into the skimmer. Now the user can have the skimmer process more or less water just by the push of a button!!!