Sorry I missed all the excitement! That's a good plan to observe the rock for a few days to see where things are. I had a difficult time aquascaping with my TBS rock, because there was so much life on it that I didn't want to cover it up!
I know you just got everything, but I would suggest that you glue the tree sponges to a hard substrate. If you keep it in the sand the base is sure to die and possibly, if not surely, spread to the rest of the sponge.
Congratulations!
