What should I do in this case?
1. Don't panic.
2. Nothing. At least not right away. Odds are power will come back soon, if not check out #3.
3. Water circulation. I use a simple DC to AC inverter (
dc to ac inverter - Google Product Search ) to plug into my car's cigarette lighter. I then plug an short extension cord into the converter and run it into the house (from my garage). I use a low wattage Hydor Koralia (
powerhead koralia - Google Product Search )powerhead plugged into the extension cord to keep water circulating in the tank. None of the Koralia products should come even close to over taxing the inverter, but never plug a device into the inverter that has a higher wattage rating than the inverter.
4. Temperature concerns. I find that my tank at about 135 gallons doesn't flux that much even with the power out, extreme conditions aside. At tank temps of 85 to 88 your corals and fish should be fine. If things start approaching 90, its time to float some bags of ice or prepare for some losses. There is no good solution unless you have a chiller and a generator to run the chiller. The chiller is WAY too much for a simple car inverter, well beyond the scope of my response. Due to the use of a low wattage koralia, I was also able to run a small low wattage fan to blow across the top of the tank.
4. Lighting. Your ok with out lights for a couple days. Things may not look great but again, with out a generator as a power source, your out of luck until the city power comes back.
5. Lastly, again, worth repeating, don't panic. Regardless of what happens, safety is first don't start changing things while the power is off. Oh, and be sure to monitor water levels in things like sumps. Some people don't realize when the power is off, water can fill a sump and potentially over flow. Did I mention, don't panic? Great. Best of luck. -PC