I used everything from my 55 in my 75. I had a sump tank on my 55, so I had about 65-70 gallons of water to use. I got with David from Crystal Clear for advise on the best way to move, but basically I transfered all the water and sand to the new tank, then topped it off with new salt water resulting in something like a weekly water change (65-70 gals of "mature" water with about 10 gallons of "new" water). Waited a few days then I added my sump and again added new water to top it off. All of the fish and corals seems to be doing great. We probably have run into each other, I or my wife are in Crystal Clear at least once a week