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What Is A Berlin Filter?


The Berlin Filtration System used in many saltwater aquariums was invented in, of all places, Germany. The original Berlin System is still the preferred filtration system of many reef tank purists and consists of:

The Live Rock in a Berlin System serves two purposes:

  • Biological Filter - The surface of the Live Rock serves as a platform for the nitrifying bacteria (nitrosoma and nitrobacter) which convert the ammonia produced in your tank into nitrites and then nitrates.

  • Natural Nitrate Reduction - The multitude of small "cells" in Live Rock create the perfect oxygen free place for anaerobic bacteria to grow. Anaerobic bacteria converts the nitrates in the tank water into nitrogen gas, which is eventually vented into the atmosphere.

The protein skimmer is the primary filter in a Berlin filter, removing D.O.C.s (Dissolved Organic Compounds) from the tank water. D.O.C.'s are, for the most part, proteins which would normally be broken down and processed by the bacteria in the Biological Filter. D.O.C.'s are created by fish and invertebrate detritus and uneaten food. Since live rock is not the most efficient (surface area/lb or /cu.ft.) biological filter platform, skimming most of the proteins from the tank water helps the relatively small bacteria population to keep up with the tank's bioload.

The original Berlin Filter System incorporated Metal Halide lighting. However, any reef tank lighting system (i.e. Power Compact, fluorescent, etc.) would work as well, as long as the spectrum and wattage were comparable.

As with any filtration system, Berlin Filters have their own advantages and disadvantages.



  • Limited tank occupant capacity.

The Berlin Filter is an efficient filtration method which has proven itself over the years. The filter is simple, inexpensive to install and will work well for most reef systems if the biological filter capacity is not exceeded.

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