We are using an APC UPS (uninterrupted power supply) on our tank. However, we only have the minimum hooked up to come on if the power goes out and that is the pump that circulates water for the tank and sump. Fish and coral do not have to have light for the period of time the power might be out (ie. hour or two). It'd be like bad storm in nature. However, it would be good to keep some sort of circulation going. A computer takes up a lot of power, so if you calculate it out, you might find that you will get more time than what is stated for a computer if you are running just a pump or couple small powerheads off the UPS. APC actually had one of their magazines come out with a man on the front and a huge aquarium behind him saying that he uses their computer backup unit for such power outages. Of course, he had a big UPS that is made for more like huge servers. I have a 55 gallon so did not need such a monsterous one. Go out to the APC website and see what they have. You might even want to call them and tell them what you want to use on it...have the specs of your equipment you plan to hook up to it...and they will probably be able to give you some good advice. I bought mine at
www.pagecomputers.com At the time (april 2002), they had the best prices on them. I believe we have the APC Back-UPS 650VA. Not cheap, but worth the peace of mind for me.
There have been some stories of peoples electricity going out for a full day with no backup system for their tank with no ill affects. One guy up north just wrapped the tank in blankets to keep the temperature up (since it was the middle of winter) and all was well. So, to each his own.
