Water temperature is what changes the fastest and is what kills things first. 200 gallons will hold heat for quite a while if the house is still heated. If both don't have power you don't have too long. My guess would be some losses starting at 24 hours and getting worse from there.
If your there and can wrap blankets, add an air stone, etc you might have 48 hours before the badness begins.
Good question.
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