Help with HOB Protein skimmer pro pack

[allyhorse]

I have a pro pack HOB protein skimmer. I got the thing new on ebay but no directions. I hooked it up like the picture. It makes bubbles and air flow is all the way up but I have never had to clean the cup, nothing in it at all. I have a 55 gal reef tank with about 50 lbs of live rock and 5 fish. It has been set up for about 4 months. Is there just nothing there yet or is something wrong with skimmer? I had a huge reef tank years ago and I was always cleaning it out.

Thanks
Ally