Mike, his presentation really opened my eyes. He got into some really detailed chemistry formulas, but also made it pretty easy to understand. Basically, if you keep up with proper maintenance...do regular pwc
's, use GAC
and change it regularly (he recommended aprox 1 gram/gal
of each and change it every 2 weeks), the kind of skimmer you use makes very little difference in the overall water chemistry. In fact, there was little difference between running a skimmer and no skimmer at all.
A skimmer mostly removes calcium carbonate, magnesium and phosphate, and that comes from the micro organisms (which have a calcium shell and consume phosphate) that are skimmed out.