Well you could probably get some locally and with that its not "live" so you can add the rock as you want without curing it or worrying about hitch hikers. It doesn't have to be all at once.
Theres some real benefit to having rock in the tank, it acts as a major part of your filtration and the more the better (within reason)
180g Reef - 60g Rimless Reef -90G FOWLR- 125g Malawi Cichlids- 40b REEF- 34g Fresh Planted-working on- 20L FOWLR- working on
I have a mix of many different saltwater fish amongst my tanks, but I love my Tangs most of all.