From your description it sounds a lot like you have a Coralife SUper Skimmer........A manual for it can be downloaded from the internet, but I would demand a manual and all the paper work that came with everything that you purchased. Seems they do not want you to be tank savy and learn anything so they can get the money to do service and maintenance .
That said, to reduce bubbles you need to make sure the outflow tube (tube that water going back intot he tank flows from is not below the surface of the tanks water level. The pump should be raised as high as possible in the water, for best results..........DO NOT alter the air intake tube or put a valve on it thinking you can control it..........and also do not alter the little bleed vent on the top of the outflow tube.........Depending on setup height of pump on skimmer etc if the water level in your tank needs topping off that can make micro bubbles as well..........turn the red knob on the adjuster fully clockwise. This should stop all outflow of water......then slowly open the red knob turning CCW while looking at the reaction chamber of the skimmer (long clear tube under collection cup) until you adjust the tops of the bubbly water so its about 1/2 to 3/4" below the funnel portion of the collection cup. In that position your knobs little red pointer (have to look close to see it but its there) its probbaly going to be at or around the 5 to 7 oclock position. This will give you a drier skim, and the cup wil not fill as fast with wet skim...........If your outflow tube is not in contact with the water, and your bubble column is set as described above, just close off red knob a touch more........If you look at the bottom of the reaction chamber where the air infuser is discharging all the bubbles into the reaction chamber, you should see 99.9% of the infused bubbles rising upwards into the collection cup area............if you notice a great deal of bubbles flowoing down under the infuser and towards the outflow port at the bottom, clos eoff red knob slightly. Some coralife skimmers also come with a valve to restrict water flow.....usually not needed. You can also slide the skimmer up a bit higher in its bracket, as its possible it slid down which makes it lower in the water of the tank and will also cause you the bubble and cup filling problems.......Best results is outflow tube barely touching or not touching the water level in the tank, and the pump within 2 inches or so below water level of tank.
Just to clarify the settings on the skimmer, the original setup instructions for the most part are WRONG. Coralife will tell you that as well as they screwed up with the dimensions and setup proceedures. They have not placed the new setup instructions in the newly packaged skimmers yet, and the setting of outflow and pump heights is what has been changed.........They expect to have a downloaded version of the new instructions on their website shortly, but the original and handy to have instructions are available from a few websites, which I would get as they are good to have for basic info on the skimmer and what causes such and such to happen........Like I said its only their setup dimensions that are off, so the basic instuctions still have value.
