Protein Skimmer or Foam
Technical Data On Protein Skimmer / Fractionator
How Protein Skimming Works
Protein skimming is the term most commonly used by aquarium and aquaculture professionals to describe the removal of suspended and dissolved waste from fish by means of air floatation.
To be effective, the protein skimming process requires a contact column or reaction chamber in which the air and the water can interact. 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 provides the air and water interfaces.
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 live support system.
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 disinfectant properties, makes skimming possibly the best component one could add to a modern life support system.
Different types of Skimmers
Venturi skimmers uses a venturi injector to create air bubbles. These skimmers tend to be shorter than air driven counter-current skimmers, and require a powerful pump to drive the venturi valve. When matched with a high performance pump, these injectors create large volumes of fine bubbles. The bubble quality tends to be very good, and this aerated mixture is often injected into a reaction chamber in a swirling fashion to maximize contact times.
Air driven counter-current Skimmers
Air driven skimmers are the original types of skimmer designed for the home pond, and fortunately they are one of the most efficient. However, they also require the most frequent maintenance, and can be costly. These skimmers use air diffusers and a powerful air pump to produce their bubbles. These skimmers have excellent foam volume and consistency when operated with air stones. Depending on the organic load of the pond, air stones should be checked and replaced, as well as air pump diaphragms. The height of a counter-current skimmer is critical due to the fact that the water and air bubbles must interact over a set distance and time, and a skimmer to short will not meet the criteria.