ajbully... where do you have your collection cup set at? Really high, or really low? What color is the skimmate you're collecting? Just curious, because if the cup is set too high (very little skimmate, if any, in the cup over 24 hours) I've found a lot of the "foam" the skimmer creates is just dumped back into the tank.
Right now the collection cup is set really high and it's not producing much skimmate. I originally had it set very low and it was producing a very watery skimmate.