This has been a very good and enightning discussion.
I have been using Canadian Peat Moss and originally thought it was not very acidic.
Have discovered that if I saturate it, let it sit 2 weeks or so and then I run RO water and percolate the peat in an old electric coffee maker, I get good acidic water, low TDS and very nice tannic acid from it.
It’s so dark sometimes that I pour 11 cups of percolated into 4 gallons of RO water.
Now I’m getting a fairly stable mix of the range of pH 5 to 5.5
The pH does creep up slowly since I cant replicate a Malasian swamp for constant flow seepage, but it is easy to control.