If you put driftwood bought from a commercial supplier in your tank without preparing it properly first, do you run the risk of introducing something foreign into your tank that can harm your fish? I mean, I know you may want to soak out some of the tanins so your tank doesnt turn brown, but is there any other purpose for preparing driftwood? I ask because I put a large piece of driftwood in one of my tanks about a month ago and recently my fish have been acting sluggish between water changes, which I do very frequently. The water parameters are all fine, but a couple days after a change they all act very sluggish, and the only thing thats different is the driftwood.