Overskimming is normally not a worry with the average hobbist. Since I will be running 5 skimmers in my system I will also have a dosing program. as long as you do adequate water changes you should not have a problem. There are two camps on this issue of overskimming one that feels it is possible to overskim and one that feels it is not possible with the equipment used by hobbist. I would not worry, but do test for depleted iodide, strotium, magnesium, calcium, and watch your alkalinity levels. good luck and keep us posted. (skimming is good, overskimming not to worry, water changes a must).