I set the float switches in the left sump, by that I mean left of the the skimmer and the fine filter. I set my level under the top edge of the tank and adjusted the skimmer using the skimmer gate until I get a good foam level going, then adjusted the float switches accordingly. My level is currently two notches down from the top of level window. Other than filling the fresh water reservoir, my ATO has been fairly maintenance free. Hope that helps.
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