You can use peat moss found at garden centers as long as it's pure peat moss with no fertilizer or additives - it's easy to find. I throw mine in an old nylon and place it in the Aquaclear filiter - a "peat bomb" - works great. Clean, lightly-parboiled oak leaves are great too, especially if you want to place them in the tank as loose litter to make apistos and rams feel at home. And, of course drift wood will also leach tannins that will make many fish happy. Have fun!