For the past month, my skimmer has not produced skimmate. It is a sea life system, in sump with live rock and the pump is a 7 mag drive. It makes bubbles that prematurely pop before the foam reaches the collection cup. I have been adjusting the air flow to no avail. Pump and skimmer have been cleaned. Any ideas on how to fix it? Tank is a 29 gal with 20 gal sump. Thanx! Moon Jelly.