Planted Tank Guru
Join Date: Jul 2010
Location: British Columbia, Canada
Yes you can. But be prepared for tannins leaching into the water from the peat. It will turn your water tea-colored, but many people like that and it doesn't bother the fish.
But why use peat ? What's your pH now and why do you feel the need to lower it ?
But if you really want to use peat, to produce soft, acidic water, remember to change it out for fresh new peat every few weeks, as it can lose it's effectiveness.