Click the following link for FAQ’s on this issue.  This is a common and normal issue typically associated with either sponge being on your rock that despite being pre-cured would smell like ammonia or if your rock smells like rotten eggs, that’s typically because you have put it into a tank with too little or no oxygen.  Even with heavy circulation, the absence of heavy oxygenation on new rock results in a rotten egg type smell.  This is easily taken care of so let us know if you need further help.  This link should answer all your questions though.

http://www.oceanproaquatics.com/shop/activekb/index.php?query=smells&ToDo=search