Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Oak leaves, bark, or wood.
Peat moss from the garden center, but make sure it has no fertilizers or wetting agents. As little as 1 cup in a larger tank (45 gallon and up) or a fraction of a cup in smaller tanks. Recipe is very flexible.
Whatever you use, take it out when the color is right, unless you are within a few days of a water change.
Caution: I used Quercus douglasii (Blue Oak) and the water turned wine red, so dark I could not see through it. This was a lot of bark, though, not just a few chips.