The problem often is that your rock only has a 'skin' of bacteria, ditto the sand. You say you have a bunch of fish. Ordinarily with a tank with just-barely cycling you'd use a cUC to break in the sandbed for four weeks before installing one fish.
That said, I've been in that pickle in a tank move, and all I can say is if you do it, hover over that tank with dailly or twice daily ammonia testing (Prime can screw that test, I have heard, but ask) and I'd do 20% water changes weekly, just to keep it safe, while feeding no more than what will let each fish fill its mouth once daily---no leftover food; and get a good CUC in there including nassarius. Start a log book and watch trends in your test results: don't let a reading get out of the good zone before you nudge it back. Good params for most tanks are in my sig line, if that helps.