When I do a big water exchange alot of times some of my corals stick out of the water. I have a frogspawn which is very similar to a torch that does fine iff i spash it with water every minute or so. Usually it is out of the water for atleast 3 to 4 minutes so I would think the torch would be fine. They can handle it better because they can almost fully retract the flesh on them that some big bubbles and things cant. The only coral I worry about and sometimes move to the sand is the bubble because the flesh saggs down on it and im afraid it is starting to pull from the skelaton. However 20 gallons is planty for a regular water changes on a 92 gallon. that is actually a fairly large water change and any more might bother the torch, not because of it being out of the water, but because of the water conditions changing so fast. That is more than a 20% change and unless you are trying to remove some kind of poision that might have came from a poisiones fish dying or anenome, that is plenty. Unless it is a emergency don't do more than that or you can disrupt natural proccesses in your tank, and stress fish and corals. Just do more water changes rather than one huge one. It will keep things from stressing and remove nitrates slowly so everything has time to adjust to the change.
