I use the Red Sea in the blue bucket, NOT the Pro. It's at natural sea water levels which I like. I don't want the spike caused by the elevated alk and Ca in the "Pro". If you're not dosing 2-part, kalk or have a Ca reactor to keep your levels stable then you would want the extra alk & Ca to replace was is taken up, IMO...Also, fwiw, The Tropic Marin Pro is also at NSW levels and I used to use it until I heard that they released a few bad batches that crashed some tanks...never figured out what crashed my last tank but I was using Tropic Marin at the time and the more wc's I did to save the tank...the more things got worse...