Protein skimmers are the heart of marine water aquarium filtration. They remove protein that is permanently released into the water by micro organisms, invertebrates and fish. The powerful and economic skimmers remove particles and floating matter, and they aerate the aquarium. The extremely small and space saving sera marin Protein Skimmer PS 130 is one of the smallest skimmers. It is ideal for nano aquariums up to 130 liters (34 US gal.). Just like the slightly larger sera marin Protein Skimmer PS 200, it contains an energy saving dispergator pump integrated in the casing of the unit that by itself draws in air and blends it with aquarium water. Both units can easily be attached to the inside of the aquarium by a holder bracket adjustable in height. Air and water flow are easy to adjust. The sera marin Protein Skimmer 400 HO is suitable for aquariums up to 400 liters (106 US gal.) and can be flexibly used. It is suitable both as a hang-on skimmer and in a filter underneath the aquarium (sump). It is therefore optimally suitable for all aquarists that wish to switch over from freshwater aquariums to marine water aquariums. The larger sera marin Protein Skimmer 600 S for aquarium cabinet filters (filter sumps) is easy to use and suitable for aquariums up to 600 liters (159 US gal.).