What Is Aquarium Protein Skimming?
Of the many possible methods for reducing levels of organic matter in aquarium water, one of the simpler and more convenient is foam fractionation, or protein skimming. Protein skimming is a filtration method used to remove dissolved organic compounds before they break down into toxic ammonia and nitrite compounds. In a process analogous to the production of sea foam in surf, injection of air bubbles into the aquarium water creates a meringuelike foam when organic molecules collect at the air-water interfaces of the bubbles. This foam is captured in the collection cup and disposed of.
Foam fractionation is an important part of the successful maintenance of a marine aquarium. It is the only method available that physically removes organic pollutants from the water. All other techniques simply sequester pollution within filter media, which are then removed and replenished with fresh media. Meanwhile, pollutant molecules may be constantly exchanged between the media and the aquarium water, reducing the overall effectiveness of the filtration system. For marine aquariums, foam fractionation is a practical and simple way to control this organic pollution.
Which Aquarium Protein Skimmer Should I Buy?
All the protein skimmers listed on this site have a recommended size of tank for use with. Choosing a protein skimmer that is slightly larger than necessary is better than choosing one that is slightly smaller than necessary; most reef-keeping experts agree that it is difficult to overskim an aquarium. Down-draft style protein skimmers, such as the ETSS Protein Skimmers, can overskim a tank. Overskimming using airstone or venturi driven skimmers of reasonable size is not likely.
There are four basic types of aquarium skimmer designs:
Needle Wheel Protein Skimmers
Needle Wheel protein skimmers, such as the Aqua Medic Turboflotor, replaces the impeller in your protein skimmer pump needle wheel impeller. Air is drawn directly into the pump and the needle wheel chops the water and air into a fine mixture. The end result is that it works similarly to a Venturi design, it's just a different method of injecting the air into the water. These protein skimmers generally are supplied with a specialized pump for the application.
Venturi Protein Skimmers
Venturi protein skimmers, such as the Red Sea Protein Skimmers, use a venturi valve to produce a mix of water and fine bubbles. Therefore, there is nothing to replace, and adjustments may not have to be made as frequently to keep the protein skimmer working correctly. Venturi protein skimmers are also often designed to create a spinning vortex of water and air inside the protein skimmer to maximize contact time between the air and water without the necessity of a tall column. Thus a venturi protein skimmer for a given size tank will always be smaller than other protein skimmers of comparable performance. The small size means that the venturi protein skimmer can easily be hidden underneath the tank and will leave more room in the cabinet for other equipment.
Downdraft Protein Skimmers
The Down-draft protein skimmer operates by using a high pressure stream of water injected downward into a column of plastic media, like bio balls, to suck air into the water stream and break the air up into tiny bubbles.
Air-driven Protein Skimmers
Air-driven protein skimmers (also called counter current protein skimmers) use a wooden or glass airstone to produce bubbles in a column of water. Air driven skimmers require periodic (monthly) replacement of the airstones, a strong air pump to drive the airstones, and a small water pump to move water in and out of the protein skimmer.