Question about wet/dry filter w/protein skimmer

[warden]

I am setting up a wet/dry filter with a built in protein skimmer on a 90gal tank. The instruction say to put the skimmer box just below the water surface. Does that mean the bottom of the slits just below the water? I am having trouble getting the water levels constant. Any suggestions? :notsure:

 

[sly]

Do you know what model system you are using? It would help in getting an answer...

 

[warden]

It is a Pro 150 Series Wet/Dry made by Pro Clear Aquatics Systems. Any help would be appreciated. Thanks.