I think on the 9015 it's recommended to take the blue screw all the way out to take full advatage of the skimmers pump. The longer neck on the 9015 allows this while if you did that on a 9010 you would fill the cup up quick and not skim as well.
Skimmers in general all work better when the necks clean. I clean mine good every other day. The Tunze is alot easier to clean than the superskimmer I previously had. Just pop it off, scrub and put back on, no cutting the skimmer off and twisting things off.