Learn about protein skimming, why it's important, and which aquarists should use it.
Protein skimming is a water purification method used with many saltwater aquariums. Skimming removes dissolved and particulate organic matter from your aquarium’s water and provides increased aeration.
Why Don’t You Want Excess Organic Matter in Your Water?
Organic compounds are those that contain both carbon and hydrogen (and can also contain other additional atoms). Frequently these compounds contain nitrogen or phosphorous and if these compounds are left in your water, they can be broken down to form nitrates or phosphates. Additionally, metals can bind to organic materials making them more toxic and/or soluble. For some metals, this is not harmful, but for others (like copper) if the concentration gets too high, your aquarium inhabitants will suffer. Finally, toxins that are released by some species are organic compounds.
How is Protein Skimming Different from Normal Filtering?
Protein skimming is a form of mechanical filtration, but it is different from standard filtration methods in several ways:
The materials a skimmer removes are physically removed from contact with the water. In traditional mechanical filters, the uneaten food, waste, etc. are trapped, but are still left in contact with the water. With a protein skimmer, the organic materials are moved to a separate holding container where they can be removed by the aquarist.
Protein skimmers remove particles that are molecular-sized. Typical mechanical filters remove particulates that are millimeter-sized. Skimmers operate on a much smaller level.
How Does Protein Skimming Work?
Skimmers generally consist of a tube with a collection cup on top. Tiny bubbles move up and down this tube (tiny bubbles are used because they have a large surface to volume ratio). As they move, organic materials suspended in the water column adhere to the surfaces of the bubbles. At the top of the tube, the bubbles come together to form a foam. This foam is then forced up the tube and is dumped into the collection cup at the top. In this way, the water that leaves the protein skimmer has much of its organic materials stripped. The organic materials in the collection cup form a waste called effluent and a brine solution is also collected in the cup (you need to periodically check your salinity because skimming does remove some salts). This waste is then manually disposed of by the aquarist.
What are the Benefits of Protein Skimming?
The primary benefit is the removal of organic compounds and waste from your aquarium’s water. Dissolved compounds and very small particulate matter that cannot be removed by typical mechanical filtration are removed via protein skimming.
A secondary (but still very important) benefit is that when water enters the protein skimmer, it becomes saturated (or close to saturated) with oxygen due to the large amount of bubbles in the tube. Oxygenating the water has the obvious benefit of replicating the high-oxygen environments many of our saltwater inhabitants are used to.
Who Should Use Protein Skimmers?
Many people choose not to use skimmers and their tanks are just fine, but as a general rule, you will want to use one if you have a reef tank or a tank with invertebrates. If you have a FOWLR (fish only with live rock) or a marine tank, then the need for a protein skimmer is greatly reduced. It certainly will not harm anything (other than the added cost to your wallet) to have one with a FOWLR setup. In fact, it can be useful in removing the thin film that can form on the surface and it will increase the oxygen concentration of your water which your fish will appreciate.
Protein skimming can be a very effective way to remove dissolve or particulate organic materials from your saltwater aquarium. There are many different styles to choose from, but they all basically do the same thing. Refer to the Further Reading section for more information about each specific type of skimmer.