Well, my concern was that this has been ongoing for quite some time now. I was hoping that by adding the gasket I might start to see some foam at least attempting to rise. I will wait and see if anything changes, since I have nothing else to try until the bioball comes.
I guess the part that blew my mind was that when I scrub the rocks and make the water completely clouding with detritus and algae, then the skimmer actually foams and pulls stuff into the cup. But after a few minutes, nothing again...
I have been running this skimmer for the entire 2 1/2 years that I have had the tank running and back in the day I used to get some foam and skimmate.
Yes, when I adjusted the air flow, I did just as you said. There are bubbles in the skimmer body, but they all just pop by the output...