You should be good for a couple of hours w/out any power, I lost power for 4 hours recently to no ill effects. I had a friend that lost power at his office for 36 hours (55 gallon) and he put a battery powered airpump in the tank. The water got to about 60 degrees and he lost a few things, after the power came back on and we took out the dead we added a teaspoon of sugar and didnt lose anything else and looked back to normal in 2 days...This unfortunately is not the norm though, but not the exception either