Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Turface removes the KH from the water, allowing the pH in the water to drop significantly.
A little dusting of peat moss on the bottom of the tank may help acidify the substrate.
Any sort of organic matter can do this. Oak leaves, for example. Do not overdo this, just a little bit, well scattered. If you use peat moss, for example, you would still be able to see the glass between the peat moss dust.
If you want a less dusty peat moss there are pelleted peat moss in aquarium stores. The idea is to add these to the filter, but there is no reason you could not use this in the substrate, if you want. A small amount of peat moss, under the other substrate is not messy compared to using a lot of peat moss. I have used peat moss + Soil Master Select (about 50/50) for carnivorous plants. That got really messy whenever the water was disturbed.