We need a little more information than this im afraid.
What has happned to the liverock?
Does the tank have any livestock in the tank at the moment?
What other types (if any) of filtration do you have alongside the exsisting liverock.
What makes you so sure the liverock is dead?
Even reefbones (liverock that has been dried out for a few months) can be turned back into liverock again.