I've lost power many times over the years, and usually it's no big deal. My tanks have survived a full day with no power, without loosing anything or getting too hot/cold. For some reason people on the main road north of me LOVE to hit the power poles, and 2 times a year or so, somebody will take one out and it's 6-10 hours in the dark, but the fishes/corals all do fine. I do not feed them for that day and just make sure everything restarts OK when the power does come on.
The only BAD deal I had was Hurricane Ike 3 years ago when I had no power for 8-9 days. My reef did great thru day 2. Day 3,4 things started smellen odd, and I pulled the fish out. kept them in buckets with battery powered air pump. Day 5&6 the tank started getting ripe, and by days 7,8,9 it had crashed and lost 90% of the corals.
But for only 8-10 hours, i'd not worry too much, with the exception of temp.I like the fan over the tank idea, but I've since bought a large gasoline generator that'll run my main DT for days, and keep 100gals gas on hand.