Coralife DC-Controlled Square Protein Skimmer 300GCoralife DC Controlled Protein Skimmers are highly effective at removing dissolved organic compounds from aquarium water and make an effective addition to your saltwater or reef aquarium filtration system. The NEW square shaped design maintains the tapered reaction chamber but upgrades them with a larger neck to reduce buildup. New features in water and air flow adjustment allow a simple yet precise level of control.