When I moved from the 55 to the 180, I used as much of the old water as possible and also used some of Ed's water change water from his 120. I set aside about two gallons of the live sand and then took the rest in rubbermaid tubs out in the yard and washed it thoroughly with the garden hose. Just kept tipping it one way, spraying it, and draining off the water until it ran clear. Then I left it dry in the sun a few days. Once the sand was in the new tank a week or so, I added the established live sand from the old tank.
As I transferred the live rock, I swished it all in clean new saltwater. It worked out perfectly, and I never got any blooms because of the move.