have any meds been used while the tank was used as a QT? what are the dementions of this tank?
the rock you got is dry rock? if so, i would let that cure a bit then eventually add a small piece of rock or a few pieces of rubble. you'd get a nice mixture of life off that compared to a bag of live sand sold out of drfosters. if you could get a small culture of sand from a tank thats usually a good thing too. ive got a good population of spaghetti worms in my sand and thats just not something that comes out of a bag of "live sand" as well as pods and so on. i would just be sure its coming from a good friends tank, and even then inspect (QT, dip, treat if need be ) everything before putting it into your system.