Turn it up and it will move more water and break it up some...but at some point (more flow or closer to the water surface) it will likely start a vortex and suck in air. If you go with the pulse mode it will do it on every wave cycle as the water level dips down low enough/pump ramps up.
Keep in mind a protein "skimmer" isn't the same as a surface skimmer...you need a weir that will break the water surface in order mix the surface film with the water column where it can be processed by the protein skimmer. I'm not familiar with the slim skim, but if you can overflow directly into that, you would improve the efficiency of protein removal as that is essentially what is floating on the surface (your influent would have a higher concentration of proteins to remove).
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