wrote:

any time their water is 55oF or better for at least 8 days is fine. their
immunity is functional.

But you don't want it too warm, when there may be oxygenation problems. If
the fish are already using most of the available oxygen, and you stir up a
lot of half-rotted mulm, you could end up with a serious O2 shortage. It's
probably best to do it while the temperature is under 65F, and certainly
under 75F.
--
derek