I have had a Bak-Pak skimmer/refugium combo, called the Aquafuge II PS, for about 3 1/2 months. I play around with the cup position; I currently have it about where Meow said to put it. The lower it is, the more "tea" (looks like green tea) it will capture. I empty the cup while morning coffee is brewing and again when I get home from work. Generally, there is about 1" of "tea" in it. Be sure to always smell it before emptying
The manual says if the air line is making too much noise, you can attach another piece to lengthen it. I bought some 1/4" airline and an airline valve for mine to length the line by a couple of feet. I used the airline valve to join the airline pieces and to serve as an additional adjustment. During normal operation, I have both valves full open. The airline hangs down behind the tank.
The thing is really noisey. When company is over or when I just don't want to hear it for a while, I will shut off both airline valves (the one I bought and the original one at the end of the line) and deprive the pump of air. At that point, I no longer have a skimmer, just a pump for flow through the fuge, but it makes the unit very quiet.