I'm not familiar with Jebo skimmers, but you want a dry foam. If your cup is filling with tea colored water, you'll want to decrease the flow a little. If your skimmer pulls the air through the pump impeller, increasing the air will drop the water level a bit. Your skimmer effluent should be dark, nasty, and will probably stink. Most skimmers require a break in period before they really start to work right.
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