Chronically high pH... help please?
So my tap water is basically like liquid rock: pH8.6+
I've been filtering the tap water through a peat-moss funnel which brings the pH of the water down to about pH6.6-6.8. However, when I add it to the tank, the pH drifts up until it stabilizes around pH7.6. This is with Indian Almond Leaves in the tank and peat moss in the filter.
I've recently switched over to RO/DI water but the pH is only adjusting down modestly after two 20% water changes (pH 7.4 or so).
The tank set-up is for CRS and has mostly mosses, a small piece of driftwood, and tahitian moon sand.
I'd like to avoid re-doing the substrate (i.e. Aquasoil) or bringing CO2 into the equation... is there anything else that I can do? Do you guys think the RO/DI water will eventually do the trick? I'm just afraid that it lacks the proper buffering capacity to bring the pH down.
Ideally, I would aim for a pH of 6.5 to 6.8 or so. I apologize for the long post, any help and/or advice would be appreciated!!