If it still has dead debris on it, you might bleach it a few days. Pure bleach, (nothing that foams) and water, then soak in fresh water a few days, then a second fresh water soak using lots of Prime Dechlorinator, then its ready to go in your tank.....
you'd mentioned making live rock coloums at one point, I have some heavy weight cardboard 4" to 5" diameter tubes at work that would be perfect for that..... Portland cement, vermiculite and some argonite sand, and we could make you some man made rock one weekend.........
Let's do it!