You mean you have to change the airflow every so often to restart the foaming? Hmm, haven't used this skimmer, but how long has it been running, and is the system established? It does take skimmers a few days usually to get "slimed" over and start behaving normally.
Skimmer has been on for six months and just recently moved it from the main tank to the refugium below. It skims for a while quite quietly then starts making an awful noise. I have to keep adjusting it to get it to foam.
I have to adjust my every so often. All I do is turn the valve wide open so that is skimming all the way, as soon as the bubbles start to overflow I slowly turn it down until the bubbles don't flow over, then I watch it for it minute to make sure its working right. Thats about all I do to mine.