Skimming is a water purification technology that is used in many reef aquaria. It goes by a variety of different names including foam fractionation, protein skimming and, mostfrequently, just skimming. Likewise, the device itself is referred to as a skimmer, a protein skimmer or a foam fractionator. Its basic purpose is to export dissolved and particulate organic matter fromthe aquarium, with the substantial side benefit of increased aeration. Such devices have been used in other industries, such as protein purification, for many years, and many hundreds of scientificpapers discuss their use.
This article is intended to help aquarists understand how skimmers work on a molecular level. Because skimmers vary considerably in design and represent a continually evolvingtechnology, this article will not attempt to show that one design is best. In a 2002 article Frank Marini detailed many of the designs available at the time and discussed some of the design principlesfor making skimmers. In addition, this article's reference section provides additional scientific references for those who are interested in some of the engineering aspects of skimmers designed foruse in seawater.
Instead of repeating the type of information mentioned above, this article will focus in a more detailed fashion on the physical principles behind skimming. It also will helpaquarists understand what is and is not removed by skimming and whether any special supplements are needed when skimming. For those undecided on whether to use a skimmer, it may help aquarists decide whetherto use the technology and, if so, how aggressively to do so.
The sections of this article are:
* Why Export Organic Matter?
* Basic Principles Involved in Skimming
* Hydrophobicityand Hydrophilicity
* Basic Skimming Function
* The First Step: Air/Water Interfacial Area
* How Much Absorbs at the Interface?
* How to Generate Air/Water Interfacial Area