Wait, do nothing but weekly water changes, add nothing, and with time, your rock will become alive. It takes time for the dead sponges and other life forms in the rock to fully decompose. Also it take longer for the small sized life forms that have survived the transport shock to begin to regrow deep inside the rock.

If one has the patience (I dont), let the tank age for at least 6 mos before you add any new life forms. The only person I have ever heard of who has actually waited the truely proper length of time for the rock to age is Sherri A.