"In 1998, Jason Kim (owner and founder of AquaC) developed a patented process of protein skimming which has come to be known as Spray Injection. Unlike previous forms of skimming, our spray injection method enables huge amounts of air and water to be processed with a relatively small pump. Although it is a simple process, there is still some confusion as to how the spray injector works.
Imagine that you're washing your 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. That is exactly how our spray injector works."
it doesn't use what?.... regardless, it is different from the standard ones I'm use to. check out that spray nozzle and ensure it doesn't have calcium/salt buildup or any other sort of mineral build-up preventing it from properly taking in air.. ditto for wherever it is sourcing that air intake from.
http://www.f3images.com/IMD/UserManuals/AC3121.pdf
Page 2 Item # 7 is what you should be inspecting :)