Depends on the unit, the way it is designed. I've never used a Prizm, but I'd bet some maastard has. Ask this question on the General Reefkeeping Forum.

On one of my skimmers, you close down on an valve on the outlet side of the skimmer to get wetter foam (i.e. it raises the water level in the body of the skimmer); you open the vlv to get drier foam (wtr lvl in body is lower). On a different skimmer, an air vlv on the venturi was used to raise/lower the water level in the body of the skimmer (more open = more air = water level lowers in body of that skimmer; crank down on air vlv = less air = wtr lvl rises in skimmer).
..Karl