It may cause a mini cycle, I have upgraded/moved tanks several times, I set up a kiddie pool, with all old water, set up new tank with old live rock and test for a week. With all the stirring up of the old sand moving it, that is difinity going to cause a cycle and release all the nasties hidden in there (depending on how old it is) A mini cycle should be 1-2 weeks, most of your bacteria is in your live rock, (depending on how much you have and what size of tank) Used water is just that used depleted water, thats why we do water changes. It carries little to no beneficial bacteria.