There are plenty of options for a UPS (uninterruptible power supply) It really depends upon how much you intend to run off of it and for how long. The main thing you will want it connected is your pumps right? Coral and fish will encounter major problems with oxygen after the water stops circulating for long periods of time (anything more than a few hours I'd imagine). That being said it depends upon the size of your tank, the pumps and the particular set up that you have. If it's a large tank then a powerful return pump won't last very long on a battery backup but if you just have a couple of powerheads connected to it to insure water circulation in the event of a power outage then you should be able to make one work just fine depending upon your needs. Just search for battery back up, or UPS. there are options for small to large for pc's, large servers and I believe they even make them specifically for saltwater tanks. Hope that helps.