well for the bacteria to come back, that will be relatively short compaired to how long it will take for all the inverts and worms and whatnot to grow in the rock
I'm thinking that for the bacteria to come back it may take around 4-6 weeks...about the time it would take for a tank to cycle...for all the worms and stuff...probably a few months. I put some completely dry lace rock in my 55 with the same amount of live rock..the lace rock isnt any different than the live now, and its loaded with all sorts of pods, worms, even corals and stuff that just popped up that i never even put there...must have come from the other rock i guess.