I think the way you have it plumbed is part of your problem. There is too much plumbing involved and you're increasing head pressure by a lot by plumbing it so low in relation to the skimmer body. Also, do you have the MAK4 running at the same time? If so, you're probably creating too much turbulence in the skimmer chamber to reap the benefits of the needlewheel pump. try taking the MAK 4 off and remounting the 6000 right next to the skimmer body with as little plumbing as humanly possible. leave the air guest valve wide open for a couple of days and see how it does.....