First, the skimmer takes a couple of weeks to break in. Second, if you use a slime protecting chem in your water it will cause this. Use Prime instead. Third, why do you need a skimmer in a 10g tank? Seaclones are notorious for being a bad choice. However there are people who have had success with them. They need to be adjusted constantly at first and after every cleaning. If you use the slime protecter chems, they will produce micro-bubbles(like you have) and they will also overflow badly because of it(chem). Run it for a couple of weeks with no air to break it in, then slowly adjust the air till it is in the right position in the cup(according to manufacturers instructions). Then just be ready to adjust it a lot for a few days or weeks. Also if the tank is new, don't expect much skimmate in the cup for a while, there probably isn't much gunk in a new tank. With a 10g tank frequent water changes are much more important than skimming. A 10g water parameters can change drastically in a very short time.