Not sure but, I used a teaspoon of gypsum and 0.65 ounces of 5.2 ph stabilizer in my mash water... This is what I was told to use with the water in my town...
I added about a pound of fresh picked black berries. I mashed them up, put them into the secondary and transferred. Three days later I kegged it. Came out pretty good!
I was just asking myself this same question. I just started using a chest freezer with a temp control. If I want to ferment at 67 what would be appropriate external temp (temp inside the chest freezer)???