You don't need to go to a lot of effort to get the piece ready for the tank. Rinse it well with the pressure nozzle attached to the garden hose and leave it out in the sun to dry for a couple of days. The heat and rays from the sun will be more than enough to kill any bacteria.
Boiling will soften most woods and they can come apart in the tank. Just rinse it well, dry it out and while it dries, look for some decorative rocks. You'll need them to weigh down the piece in the tank.
"Fear not, my young apprentice. Just change the tank water."