I took water out of my tank, put the rocks I wanted to keep in it in there. Got another and put rocks I didn't want in another (to be sold), and put the corals in yet another and fish in another. If you're quick, you wont need agitation of the water in the buckets. If you feel you'll be a bit, add a bubbler in for the fish and a small powerhead for the corals. Be sure to take this chance to vacuum the sand as best you can in the places you haven't. This will help you get rid of a lot of potential crap and help keep phosphates, nitrates, and the potential hydrogen sulfides down in the future.