I am a bit iffy on soaking driftwood in bleach. It could soak deep into the wood then create a new problem once introduced to the tank. I usually boil my driftwood's for an entire day (6-8 hours) replacing the water once it gets really brown. Then soak for 2-3days depending on how much tannins are still seeping. Also if any tannins still leach you can always use Purigen to remove it. It has been highly effective for me.