I would never hypo a display tank, but when I moved cycled rock from a display to a 30 gallon for a hypo treatment, I never got a massive die off. My parameters never changed. I tested it with table shrimp and still never got an ammonia spike of any sort.... it was undetectable the whole time even after the volitan went in, so my biofilter remained intact. My SG was 1.009 the entire time.
Just sharing what I experienced on a number of occasions......