I put 8 ounces of Vinegar in with my Kalk top off. I skim pretty wet and have a decent evaporation rate on my 90 gallon reef, 20 gallon refugium and 15 gallon sump. Overall water volume is right around 110 gallon of water. Since adding Vinegar about 2 months ago, my Nitrates have been "0" and my PO4 is .01 or less (Hanna Handheld Photometer)
An additional benefit is my water is crystal clear, I don't run GAC or GFO. I run through about 5 gallon of makeup water a week to give you an idea of how much actual Vinegar I am dosing in my system (Approx 8 ounces a week). Hope this helps out.
Later,
Jim