It will go thru a small cycle, you will have to keep a close watch on parameters, I would not got thru all the trouble of trying to move and save all the old water, it has very little bacteria in it. Start with 50% of more of new, I also would not use the old sand, just a scoop or to, best way is to set up new tank with you lr
first first and then direct transfer. If not possible get a cheap kiddie pool and transfer everything into it and then set your new tank up. With free water, sand and old LR
and let it run for 3-4 days while testing.