After a quick skim of the thread, once again TheCanuck is correct live rock in the sence of the store baught stuff is a money grab for importers, only a few pounds is needed to seed a whole tank and "fake" live rock whether its lace rock or DIY aragocrete its all good once the tank cycles. People tote that live rock is "the" source of biofiltration but thats just not the case, the sandbed does almost all if not all the important biofiltration as the sand bed contains a heck of alot more bacteria.
Live rock ("real" or fake" or the sand bed) does not get ride of nitrates, it eliminates ammonia and nitrites (highly toxic), changing them into a less toxic chemical known as nitrates, these are then used by macro/micro algaes to grow. So adding live rock wont get rid of these things as some people say but it will make them a little less toxic and a little more removable by the macro algaes in a fuge.