How Protein Skimming Works and Why You Should Use It For Your Aquatic Applications
Protein skimming is the term most commonly used by aquarium and aquaculture professionals to describe the removal of suspended and dissolved waste from fish tanks by means of air floatation. Protein skimming is a relatively simple process which relies on the physical and chemical properties of coagulation. A summary explanation describes organic molecules (surfactants) as polar at one end and non-polar at the other. The polar end is hydrophilic "or water loving" and attracted to water molecules. The non polar portion of the molecule tends to orient their hydrophobic parts in contact with air. This surface active characteristic allows them to concentrate at air/water interfaces. To be effective, the protein skimming process requires a contact column in which air and water containing these surfactants can interact. The air and water interfaces are provided by supplying a constant injection of small bubbles to a proportional volume of water in the column and allowing them to mix and then migrate to the surface. During this migration, suspended and dissolved organic material (protein is a specific class of organic material) congregate at the air/water interfaces, with the bubbles forming a "skin" like character on their surface. At the upper levels of the column most of the water drains away leaving a concentrated residue of foam composed primarily of organic material. The skimming off of this foam waste removes it from the life support system. It is, therefore, no longer susceptible to undesirable microbiological degradation which will contribute to increased oxygen demand in an aquatic system. Protein skimming is essentially a perpetual backwashing filter. In addition, skimming enhances the oxygenation of a system both biologically and physically. Biological oxygen demand is reduced by the direct removal of biodegradable organic carbon (protein), as well as bacteria in the water column. Physically, the increased surface area provided by the injection of large volumes of air (in the form of small bubbles) into a column of water creates a condition for gas exchange. The addition of a small dose of ozone to the process, with its coagulative and disinfectant properties, makes skimming possibly the best component one could add to a modern life support system.