Very sorry to hear about your fishes, many tropical fish can handle water down to 55 if they have to but it's not good for them and many will die later of complications. I live in a hurricane zone, I always make sure my tanks will operate for several days with nothing but a battery powered air stone. Not sure how to get around the whole low temp thing. a kerosene heater would help but they are dangerous, please be careful if you get one. Heat with out electricity, unless you heat with gas, is difficult. I hope it works out, I hate to see fish die for sure.