If you check out my yahoo album, you will see a large piece of wood in the tank. I found it in my parents forest, brought it home, scrubbed and cleaned it, boiled it for 30min and put it in the tank. I was fortunate that it could wedge into the tank so floating wasnt a problem. The water turned brown for around 2 weeks I think! But mind you, i also do 50% weekly water changes. Now, the water is clear. I think it does depend on the type of wood.