As previously mentioned, in a counter-current protein skimming system, air is forced into the system under pressure and moves against the flow of the water for a while before it rises up towards the collection cup. There are various types of skimming which falls under this catergory: Adrian-Wheel/Needle-Wheel/Mesh-Wheel, Downdraft, Beckett skimmer and Spray Injection.

Specially worth mentioned here is the Spray Injection protein skimming process. Unlike other forms of skimming, spray injection method enables huge amounts of air and water to be processed with a relatively small pump. Imagine yourself  washing a car – you’ve got a bucket full of soapy water and a garden hose with a fast-moving stream of water. By placing your thumb over the end of the hose, you can disrupt the stream into a turbulent, high –pressure spray. Now direct that spray down into the bucket of water, and you’ll generate a massive amount of bubbles and air flow. This is exactly how a spray injector works.

The skimmer body acts as a water reservoir – the bucket in the example above. Water is pumped through the spray injector, which has a special nozzle that fans the water out into a pressurized spray. This spray shoots into the skimmer body, generating millions of tiny air bubbles. As the bubbles are formed, more air is sucked into the skimmer as a result of the local drop in pressure and the process continues.

 In the United States, a company, AquaC, has patented the spray injection technology since 1998 by Jason Kim. Commercial product offerings are limited to this single company. Most other forms of protein skimming rely on special valves or media to generate the air flow, and these parts quickly become clogged with salt, dust, or even mineral deposits. The spray injector by AquaC is a relatively large nozzle that resists clogging, and when combined with a pump prefilter, can be considered maintenance free.