Like volcom said, the skimmer just needs to break in. My Prizm Deluxe produced a lot of bubbles in the tank during the first few hours. I think with in a day, they were gone, and after another day or two, it started to pull brown stuff from the water. Also, during the first week, I had to adjust valve that controls the air/water mix, gradually increasing more air. If you increase it too fast, you'll usually end up with lots of clean water in your collection cup. Sometimes people complain about their collection cup actually overflowing.