'Used' live rock from an established system, i.e. still living and covered in coralline algae and other life always has the risk of potentially tank destroying pests. And bubble algae, aiptasia etc can be a real pain later on as they out-compete your coral for space.
Your best bet is to start a new tank using dry live rock, this will ensure you have a pest free system to start adding corals to. We have lots in stock :
http://www.bigreefdepot.com/Dry-Live-Rock-s/163.htm
Just make sure you do some research on how to setup/clean/cure live rock before adding it to your system. Feel free to PM, email or call if you have any questions! Welcome to the wonderful world of saltwater!
