Hope the power comes back on!
For tank temp, you can cover it with a blanket. But if you have no generator, no battery backup for your powerheads and no battery operated air pump, there is nothing you can do. The most important thing will be surface agitation in the DT to maintain dissolved oxygen in the tank. Nothing else matters more than that so agitate the tank surface as often as you can. Holding the temp steady would be the second priority and you can do this with a blanket if need be. Depending on the tank size and outside temperature, you may have enough thermal mass to get through a night. I hope for your sake the power comes up quickly!
Come morning, if you can get out, find a battery powered air pump. That is the single most important device to have in a power outage.
Good Luck and I hope you pull through!
