Dry skimmate will be dark and pastie and wet skimmate will be pea green. I would connect the air valve to the air line but leave it completely open.
hope that helps,
kurt
75gal 6x54w t5's on icecap slr's 3 blue +, 1 pro color, 1 ge 65k, 1 uvl spuer atintic, iwaki 40rlt return, mak 4 on closed loop to om super squirt, mak 3 on etss reef devil, jbj artica chiller, aquamedic calcium reactor, DIY Kalk reactor, DIY media reactor, currently running half phospahte/half carbon.
Live in Uvalde, Texas. On the fish hatchery!