How much does the water level change in the chamber where the 9002 is?
Please keep in mind that it is perfectly normal for any skimmer to produce more foam on some days and little or none on others. There are many variables that affect this, including but not limited to: feeding schedule, additives used, burrowing livestock, water changes, salinity and temperature fluctuations, and putting your hands in the tank.
The most important thing to remember is that the effects of these variables are not always immediately noticeable. In other words, if something changes today, it may not affect skimming until many hours or even days later, so the connection isn't always obvious. Making frequent adjustments can be very frustrating, because you'll never feel like you're in control. It would be like trying to catch a baseball if there was a ten hour or two day time delay between your eyes and your hands.
Try adjusting the skimmer so you have relatively dry foam. If afterwards the cup fills up with water then close the air adjustment 1/4 turn and don't do anything else. If it seems like the skim will then be too dry, and not enter the cup, resist the temptation to open up the air valve. Just wait; the foam will return. And when it does, it will be less likely to return to the watery state because you've already restricted the air supply.
I hope that helps!
