i have moved similarly to you and i used new sand. no mini-cycle. i new a guy who did the same, kept the old sand- and nitrates went through the roof! not sure if that was typical though, it was a deep sandbed that had been running for years. so i imagine it had a lot of crud built up in it. if i were you id save a half a bucket of the old sand (from top layer of your sand bed) and use new for the rest.