https://www.reef2reef.com/threads/t...ead-aka-one-against-many.230281/#post-2681445
that has good procedure, microbiology of skip cycling and actual examples too. 6 page condensed:
the only time people had losses doing this was when a pocket of waste wasn't accounted for in some way, and partial action kicked up that rotting pocket in the presence of sensitive animals. The actual process of changing out sand is harmless and we don't need the bac we are removing, nor the bac we may or may not be bringing in as sand isn't the swing vote for surface area * in every tank I can find on the board * that doesn't mean there isn't one outlier using a single pound of live rock in a system that would depend on the sand lol
for most tanks, the sand bacteria are incidental and what you do to them doesn't matter. Rinse the new sand perfectly clean to start.
you would remove fish and corals to holding buckets or tanks, live rock separately (because that's one point of waste in some tanks, its not held w fish. My own rock is kept clean enough to do so, but in the masses we found really dirty rocks among swappers so we quit housing that risk w the fish)
once the tank is down to water and sand only, rip out all the old sand as there are no delicates stacked on top of it any more
clean the whole system, if you can't do a full water change then siphon off your curr water really cleanly into a Rubbermaid before starting this procedure
reinstall the perfect rinsed new sand, as much new water as you can stand to secure, put all rocks back in after they were saltwater rinsed to get off detritus.
re acclimate corals and fish. the bacteria on your rocks and on the tank walls are just fine for carryover into the new tank.
Not accounting for huge pockets of detritus in various places is the risk, be thorough when you switch sand, not partial in action for this very reason imo.
