Depending on how old and how long cider has been drifting it's bad or really bad. The leaking tangents in ceder can kill fish when its still fresh wood in the center. Ever thou it looks old. IF ceder is a very old piece of driftwood you can use it but it decay so fast it only lasts a year or two. I had a very old piece one time for all most two years. It looked fine but when I tried to take it out for a tank redo, it was mush.