Grabbing rock off of the Carolina beaches is illegal and is not as temperate as the rock you get in your LFS. The LFS rock is from Fiji, etc....
You can get the Premium Fiji Rock at the most popular auction site on the interenet for 1.99 /lb...
I just ordered 70 lbs from there for $201 shipped via 5 day UPS
When you add live rock at a different time, it is best to just put it in a tub with a powerhead and monitor that live rock...After the spike, it should then be safe to put it in your tank