I use submerged branches from the the lake where i go fishing. there were fish swimming around it so i figured it would be safe and the water was looking nice and clear. I just put them in the bath in boiling water, scrubbed it, rinsed then let it sit in the hot water for about 20 mins. then its good to go. no tannins as it would have released them in to the lake some time ago and i didnt have the hassle of weighting it down like store bought drift wood.