I always find my own rocks and wood, but I don't necessarily advise everyone to do so. We have a nice, clean creek up the mountain that always has tons of driftwood in it. I use wood that has lost its bark but isn't rotten, thus indicating it's been in the creek long enough to have leached out its tannins and such. (All of our wood is pine and aspen, which are both fairly non-toxic once the resin leaches out) I scrub it with a wire brush then let it bake in the sun for 2-3 weeks to kill off any pathogens or aquatic critters that might be hiding out in it. I use a similar process for river rocks. If our water was not clean, I wouldn't do this.