May I throw in a related question myself re cleaning the tank? I've been trying to figure out if it is best to clean the tank (vacuum) and change water with the fish still in there. I've tried both ways--taking them out while cleaning and cleaning with them in tank and somebody ends up injured, shocked and/or dead some of the time>
Hmmm, this shouldn't really be happening. If you find you cannot do a water change without upsetting your fish, I'm wondering if your problem is one of the following:
you are taking out too much water (20-25% a week should be sufficient, or with very sensitive fish 10% twice a week)
you are changing water too infrequently (causing a great gap between tank water and tap water)
you forget to dechlorinate
you use too big a gravel vac and injure the fish- I find the mini-gravel vac is easiest to use even on quite big tank, but then I have lots of small fish