i run mine with the air-adjustment wide open. i do notice when i clean the prefilter on the venturi it will produce microbubbles for a day or so. VESKAS, is your skimmer new ? if so it will take about a week to break in then they should subside. before you heave it take it down clean it out and set it back up and let it run for a few days see if that helps. i have been running mine on my tank for over a year now and havent really had any problems i can think of. one other thing you may want to check is the seal on the maxi-jet. mine started leaking bubbles out where the rotating base part is.
hth,
chris