How much time would a fish tank last, on average, without a heater?

[JohnIsNewToReefKeeping]

Hello.
So I am planning on setting up a battery back up system with agm deep cycle batteries that will be always at 100% charged just case for what ever reason the power goes out (for the short term). So my question is how much time would a 75 gallon fish tank last on average without a heater? I know the time may vary due to the size of the room the fish tank is in and etc. but with surface agitation going on, what would be longest this fish tank can go without a heater?
I do plan on having a low watt wave-maker connected to the battery back up but having a heater connected would drain the battery really fast.

 

[hds4216]

Depends on the temperature of the room, what it's stocked with, etc. Water has a high specific heat capacity and loses heat pretty slowly. Also depends on what temp your tank normally runs on.

 

[Waters]

Unfortunately this is an impossible question to answer. If your house is 75 degrees, you can run your reef tank without using a heater at all (as some do in warmer climates). You would be better off finding out the lowest temp fish can survive without any issues, which would depend on species I assume.

 

[ca1ore]

Before owning a generator, i had a few power outages during the winter here in the Northeast. House stays warm for a while, which helps to slow tank cooling. I found my tank lost about 1 degree F per hour. Wrapping the tank with blankets helps if you think the outage is going to be longer than 6 hours.