I am kind of in the same situation except I removed some sand due to calcification in some areas. I made a couple phone calls today to BRS and a very reputable LFS and explained to them my tank setup and because my sand bed was shallow (1-1.25" ) which doesn't promote the growth of Anaerobic Bacteria they both recommended using dry sand. It was explained to me that adding the Carib Sea Alive Sand is ok for starting a new tank but the bacteria that is in the sand is not very beneficial if at all to an existing tank. Because you now have diverse bacteria colonies that exist on your rockscape, the existing bacteria will populate on the dry sand fairly quickly. If a live sand was to be added BRS did recommend a sand like Ocean Direct Live Reef Sand because of the diverse types of bacteria colonies in that sand.
I will be adding dry sand myself along with some MB7 which I already dose once a week anyways.
I just thought I would pass along this info and I am not saying this would be fine for your tank due to not knowing your setup.