Vinegar is used to lower the ph level in Kalkwasser. If left untouched, Kalk has a ph of 12.0 You should be careful dosing Kalk, its very easy to overdose and can cause havoc in your system. Always research before dosing any element and always test before adding anything. LunaWhat mix do you use? Ive heard some peeps using vinager with it, I dont. I use 1 tblesp per gallon:fish-in-a-bag: of ro. Works good for me.