Most big pet stores carry battery powered air pumps (I think they're in the $10-20 range). They turn on when the power goes out. It'll keep the water oxygenated when all your pumps turn off and the water goes stagnant. That'll buy you some time by keeping your fish and coral alive until the power comes back on. If the power goes out for more than a few hours or day, then you're probably scr*wed without some sort of back-up generator (which most of us don't have).
A Universal Power Supply (UPS). They're designed to keep computers (and other equipment) from being turned off improperly when the power goes out as well as protect them from surges. You can get a decent one for $50 or so.
i am only 15 so i dont have that much money, i cant just get it back so i will try to get a air pump, but people are spinning out in teh streets so i dont want to risk my own life and my moms b/c i have my permit
an uninterruptable power supply is just a battery back up that converts the 12 volt battery power to 120VAC. You can get a 100 to 1000 watt power inverter that will take the voltage from a car battery and convert it to 120 VAC. A car battery would run a tank for quite a while. I would not run your ligts as that will draw down the power fast.
All you need is enough wattage to run your filter to keep the tank turning over. If you are not using a biological filter in your sump you are better off as you can actually use just a few power heads to keep circulation going in the tank and run one near the top so you can off gas c02. That and a heater is all you need. Worst case scenario is you can pull the battery out of your car and get another 24 to 36 hours of coverage from that. In the meantime put the dead battery in your car and run it to the store and after a while it will be recharged and ready to go.
A battery tender will safely keep a 12 volt car battery charged for those little emergencies.
After re reading through these posts it sounds like BiggySmalls may be stuck now without power and no backup. what should be done assuming there is no battery backup? Will water changes help? What are some ideas that will help now?