For 5 to 265 gallon tanksIn Tank & In Sump Protein Skimmers.The Tunze Protein Skimmers come in a wide variety of styles. The Tunze Comline DOC Skimmers come with AC pumps. The Tunze DOC Skimmers come with controllers and DC pumps. The smaller sizes are designed to fit inside an aquarium (ideally a back compartment), and the bigger ones are in sump skimmers.