The more air you pull the less water you pull. now if you increase the air, the water slows or if you slow it, your dwell time will decrease. if you have set the skimmer up in accordance with the manufacturers specifications and you are not getting the bubbles you desire, you can (believe it or not) reduce the air intake and the flow will increase moving the bubbles lower in the chamber which increases dwell time and producing a dryer foam. The Gen-X also is only for submerged use, Also, as mentioned, you need to clean out the air intake nipple as a regular maintenance item say once a week. This can be done by using a needle without the metal neddle part and pushing warm R/O water down the air intake tube. fill it up and let set for 10 minutes or so and it will help dissolve the buildup in the nipple. then as mentions every so often pull it and soak in white vinegar. The wire thing on the impeller only serves to cut down on the air bubble size and lowers the performance of the unit. it may seem to be doing better but in fact is not as you should not need to increase the air opening to get enough air in. (I use a euroreef 250 RC and my air is 3/4 closed. if i open it all the way the bubbles only go down about half way and the recircualtion flow decreases. I know your skimmer is not the same type as mine but, hopefully you will get the idea.) Hope this helps.