The SeaClone is a skimmer that is hard to adjust. You can tinker with the air valve, but as is already mentioned, it does not do a whole lot for raising or lowering the level in the skimmer. Maybe you can trying putting an air pump where the air valve would be

I've never tried this on mine, but I am just speculating, and if you have a pump lying around, it couldn't hurt to try. My thinking is that by forcing more air through the venturi, you will get more foam in the bubble chamber, thus raising the water level in the skimmer.
Be sure to constantly clean the inside of the neck of the skimmer cup though, because the SeaClone does skim dry gunk out.