I do want to apologize for overreacting a bit in this thread and point out that I don't disagree the other posters completely, either. My girl DID pass away while still in QT and was shipped in the mail about a month or so before the incident and was still recovering from fin damage she got during shipping from what I believe was tailbiting caused by stress from shipping. My other 4 fish handled it just fine including my other two girls which were shipped at the same time, but they were from a separate spawn. Genetics may have been a factor in her sickness.
The power outage caused a 3 degree drop in an hour (the room was about 65 degrees though) and it went back up to the normal temp in about 3 hours. I do agree that they can handle fluctuations when they are healthy, but I think it's best to insulate it in some way so that the decrease in temp happens slower. Generally, a 1 degree change should not happen faster than one hour but most fish SHOULD do fine.
My girl was obviously the exception but it is a bit of a touchy subject for me. She was my favorite and I would hate for others to have to go through what Okami and myself went through.
So again, I do apologize for my overreaction but I do hope that you can find something that works for you and your fish. Loss, obviously, is not fun and I am only concerned about their safety, even though I may be a bit over concerned.