Automatic power failure switch

[Matt T.]

I just made an auto power failure switch to keep the water circulating on twelve volt DC batteries, that are (for now) solar charged. When the power fails, the power switches to the batteries, and back to 110 VAC when it resumes. I made it for about $30.00 (minus the 12V pumps), and it seems to work very reliably. I guess it would be possible to use an inverter, but I am thinking the 110V AC pumps might drain the batteries quicker? The principle is of this switch is very simple. I thought about just running an air pump, but that only takes care of the fish. What about the bacteria? Thinking the tank cycling ever 15 min. would keep plenty of oxygen throughout the system to support 23 bluegill alive in 200 gallon tank. Any thoughts out there?