Saltwater Filtration Systems: Protein skimmers
© Winston Vaughan Schoenfeld
Protein foam skimmers are one of the most effective filtration devices made. They are external to the aquarium, and utilize a rather simplistic phenomenon. Click here to see a diagram of a basic protein skimmer setup.
As you can see in the picture, protein skimmers consist of a main cylindrical unit, which contains an air stone. The air stone provides fine bubbles which slowly rise to the top of the cylinder, collecting proteins and other organic compounds on their surface. These tiny bubbles, 0.5mm to 1.0mm in diameter, congregate at the surface of the water, and are eventually collected, along with the removed proteins, in a container at the top of the protein skimmer. The main advantage of protein foam skimmers is that they remove proteins and other organic compounds from the aquarium before they have a chance to break down and foul the water. Unfortunately, this also means that some beneficial organics will be removed from the aquarium as well. Factors which dictate the efficiency of a protein skimmer are bubble size, air flow rate, and the active contact time of the bubbles in the skimmer. The desired bubble size is between 0.5 and 1.0 mm. This maximizes the surface area of the bubbles, without considerably lowering their buoyancy. Air flow rate dictates the relative ratio of water to air bubbles in the protein skimmer. The recommended air flow rate for protein foam skimmers is around 1.8 cm/sec per cm^2 of cross-sectional area of the main cylinder of the protein skimmer. Having the correct flow rate will increase the skimmer's efficiency by creating a good foam without compromising the active surface area of the bubbles. The active contact time of the bubbles is generally controlled by two factors - the height of the protein skimmer's main cylinder, and the flow rate of the water through the skimmer. There is no specific "golden" value for these since they are a strong function of the particular characteristics of each protein skimmer and aquarium setup.
When used correctly, protein skimmers can be a very beneficial component of a saltwater aquarium. They are used in both basic saltwater and reef aquariums. I do not recommend relying on a protein skimmer alone for filtration, but rather to use it as a supplement to a wet/dry or undergravel filter.
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