What you mention is one of the reasons I am looking for an alternative for peat. At the moment I mostly use oak leaves and some peat I bought long ago, but I don’t want to buy new peat. That would be hypocritical.
It is of course a small quantity, but a lot of small stones make a mountain.
You said the main reason for acidifying water is the anti-bacterial and anti-fungal effect of low pH. At university where I am studying I learn that fungi grow optimally at low pH. In a practical course we had to grow yeast from orchard soil in medium with pH 4,5. This, coincidentally, is the pH I like to keep my paros at. How does this correspond to what you said? Is it only the bacteria that matter then? In that case, couldn’t we just pour in some kind of antibioticum? And do you know which specific bacteria are harmful for our paros?
With google I found this article. In this experiment the researchers examined relationship between soil pH and bacterial and fungal growth. Apparently at pH 4 bacterial growth declined with 90% with respect to pH above 7. Fungal growth, on the other hand, showed a maximum at pH 4,5(and declined sharply at pH 4!).
As I said before, bacteria and fungi should not be generalised, so generally reduced bacterial and fungal growth does not mean the harmful organisms in question are inhibited by (very) low pH. Also, English soil is not the same as a Bornean swap. Still, I find this quite interesting.