X2.
I once kept, about 12 years ago, a FO 30 gal tank with more than 12 fishes for more than 4 years with all fishes thriving. Just had a 1" sand bed, a few rocks I collected from the beach (I lived in the Caribbean by that time) and a HOT with two biowheels. My ammonia, nitrites and nitrates...
You can leave a car battery (or a few parallel batteries http://www.allaboutcircuits.com/vol_6/chpt_3/3.html) connected to a power inverter, connected to an automatic transfer switch http://www.pacificgeek.com/product.asp?c=216&s=1066&ID=21961&P=F as the secondary source.
Test everything before...