The water level INSIDE your skimmer needs to be 6.5" to 7.5" and that may be part of the problem. Other is the NO3POx will cause wet, and sometimes slimy, skim mate. I would raise the water level inside your skimmer and open the gate valve until the bubbles are at the neck of the skimmer, where the cup connects, and not flowing over. Try that and let me know how it works.