The Comline® DOC Skimmer 9004 is designed for use in seawater up to 250 liters (66 US gal.). It operates according to the TUNZE® flash skimming principle and acquires the water through an efficient surface suction with a surface film removal, and can therefore also be used as a "stand-alone" solution in the aquarium. The TUNZE® Foamer generates large volumes of fine air bubbles with a diameter of between .1 and .3 mm (.004 - .012 in.) and is especially quiet during operation. The Comline® DOC Skimmer with a magnet holder for glass up to a thickness of 12 mm (1/2") is supplied installation-ready.