The Berlin Method of biological filtration is method for keeping an aquarium, typically a saltwater aquarium, clean. It is basically the use of ample live rock (rock with live marine organisms on or in it) in a refugium or tank. Most often a separate tank containing a large amount of live rock but without fish or corals is linked to the main aquarium via pumps and tubes. No substrate is used in a Berlin setup to facilitate the vacuuming of debris, although a deep sand bed, biological filter setup may be used in conjunction with the Berlin. A protein skimmer is used to remove organic solids. The theory is that anaerobic bacteria deep within the rock convert nitrate to free nitrogen gas. The article is about the separation process. ... For other uses, see Aquarium (disambiguation). ... It has been suggested that this article or section be merged with Marine aquarium. ... Live rock is a usually coralline rock with marine organisms living on or within the rock, and is a term used mainly in the aquarium trade. ... Orders Scleractinia Corals are gastrovascular marine cnidarians (phylum Cnidaria; class Anthozoa) existing as small sea anemone-like polyps, typically forming colonies of many individuals. ... The word substrate can mean the following: In biochemistry, a substrate is a molecule which is acted upon by an enzyme. ... A deep sand bed (sometimes abbreviated DSB) is a filtration method used in some saltwater aquariums. ... This article needs to be cleaned up to conform to a higher standard of quality. ... Anaerobic is a technical word which literally means without air, as opposed to aerobic. ... Subgroups Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular: bacterium) are a major group of living organisms. ...