I don't have a skimmer built yet...just my sump for now, and my turnover rate and water flow are no problem. My LFS only tests for the basic stuff...PH, Nitrate, Nitrite, Ak....They don't test for Ca ro SG. I use Instant Ocean salt and have been since the beginning of my setup, and can test my own SG...I do water changes weekly....around 12 - 15%, and only use ro/di water. When I get my water tested at the LFS everything comes out very stable and also rarely seems to fluctuate.