[Scales]

Mike: I can't explain with certainty why your skimmer is overflowing, but the water level in my ER (dual pumps) will rise quickly and overflow if there is any restriction on the air flow. This happens when I run FW/vinegar through the air lines as maintenance...the overfowing can be duplicated by simply putting my thumb over the end of one of the the air tubes. I suspect (without any technical data to support my hypothesis) that the restriction of the air results in a corresponding increase in the water flow to an extent that cannot be handled by the skimmer effluent plumbing...but I am just as likely "out to lunch" with this theory. Perhaps try to attach the O3 in a manner that does not resut in restriction (I cannot offer any constructive help in this regard as I do not run O3). Cheers.