I wouldn't do anything before fermentation is done. Ferment it then
taste it and see what it needs. What yeast are you using?? If you use
Premier Cuvee it'll ferment clean because the only organisms that will
be thriving in such a low pH environment will be the yeast that you
have added. After the fermentation is done and the wine is de-gassed ,
then you can adjust the acid levels.

Bob
wrote:
> I am making a five gallon bacth of blueberry wine. I callibrated my meter
> and measured the must and got a PH of 2.8? That seemed really low but I
> measured it twice. If I am thinking clearly the is too low and I need to
> bring the number up. I have calcium carbonate that I can use. The question
> is how much should I add?