NOTE: Live rock, whether cured at the LFS
or ordered online or uncured, will re-cure when you put it in your tank. The LR
will have nitrifying bacteria on it as long as it stays wet, but sponges and other lifeforms on the rock will die during transport. Exposure to air kills sponges instantly, and they decay in your tank, producing ammonia and nitrogen byproducts.
The liverock will help yoru tank cycle, but you will still have a waiting period while it cures or re-cures. You will have to test your levels during this time....it will just take less time than if you had only dry base rock. Good idea to put in a dead shrimp during curing anyway, to make sure your rock is doing it's job.
And you can put a submersable heater in the JBJ cube sump (the back area).