Uncured rock gives you the option of 'soft cycling', which just means you minimize the ammonia so as little dies off as possible during the initial cure...
http://www.nano-reef.com/forums/inde...owtopic=180442 This just means your hitchhikers live. People get cool fanworms and corals and polypy thingys that no one has names for. You can also cook your rock to 'clean' it of the creepy things...
http://www.canreef.com/vbulletin/showthread.php?t=44859