well depends on the skimmer you have , but for the most part they should have an air line that has a valve that you can adjust for the airbubbles, and the collection cup should have a height adjustment , well be able to help more once we know the skimmer your using
I had the model up from this! The hose that is drawing water from the tank, follow it along, I believe there will be a small black circular dial which will allow you to change the air flow. It should be close to the skimmer on the top of that pipe.