I found two nice big bits of driftwood for my set up. They are too big to bake in the oven so I've soaked them overnight in the bathtub. It was 5% bleach before dilution and can have been no more than 0.5% when diluted. The wood was very slightly bleached in colour afterwards. I gave it a thorough scrubbing and rinse, it is now drying. My slight concern is there is still a faint bleachy odour from the wood. Is this anything to be concerned about? It should fade as it dries out.