I recently filled the bottom tray of my fluval 305 with peat granuals inside filter bags, it lowered my ph from 7.6 to ~7.2 over a few weeks. but I am pretty unhappy with how yellow it turns my water. I do 30% water changes with 50/50 tapwater (~140 ppm) and distilled water. And it looks beautiful for 2-3 days and then it starts getting really yellow. My rams do seem pretty happy though. I plan on taking it out when I get my pressurized co2 set up.