I noticed below someone asked what I put in my water cooler.
Posting it here since that thread is getting buried.
I have a 5 gallon glass bottle that sits on a 2 gallon ceramic crock.
Still experimenting with the proportions and try to use up the water in the crock before replacing the bottle so the ingredients don't get too concentrated.
I have a layer of silica on the bottom of the crock (like Molly does).
Add a tablespoon of borax (20 mule team)
1/2 c. Magnesium Chloride (food-grade nigari)
I also add a dropperful of 5% Lugol's to keep the apparatus clean.
The mag is what gives it the taste and silky mouth feel of good mineral water.
But use too much and you get the runs. If I feel I overdid, I just cut it with regular filtered water.