OK so i finally upgraded my skimmer to the G4 plus..which required emptying out my sump...which was a major pain in the butt. Just a quick question...SHould the air bubbles within the protein skimmer fill the entire column? They only seem to be present above the level of the pump...so the bottom half or so of the skimmer does not have air bubbles within it. Either this is normal or I'm afraid the pump may have sucked in some sand and is not working at max capacity??? Thanks for ur help!