Would this be enough in a power outage?
 

http://www.canadiantire.ca/browse/pr...romSearch=true

Or what do you guys use as a back up?

maybe enough to run a radio but not a tank these things are never as good as they say. i use an emergency air supply, simply put, if the power goes out the pump comes on and instant oxygen to the tank

It depends. I've got one on our 8 gallon biocube to run the pump and heater. I figure it will be good for a few hours in a power outage. YMMV if you have bigger pumps, higher wattage heaters etc. I wouldn't try to run lights off it.

Id just run a koralia 3 and heater on a 50 g tank

I also found this one. I think this one might be better.
http://www.canadiantire.ca/browse/pr...romSearch=true

I've seen that one on sale for $149.99 before.

Ack that thing is pretty expensive for what it is. The "spec" sheet is pretty awful so I'm guessing a bit but I doubt that unit puts out a true sine wave. Your pumps may run properly on it they may not. I picked up a 450VA (~230W) APC unit at Costco for $35 last month, just go get a couple of those.

I have used this very unit. It powers my pump (425 gph) and heater for ~6.5 hours. It was invaluable just last week when at -21C the power failed at 9:00am and did not come ack on until 4:00pm. No one was home and it undoubtably save my tank.

During the same time our pipes froze but my fish were fine.

Generators are great, but what if you are not home or on holiday?

IT must have a bigger battery than I thought then, maybe not a bad deal. How many watts is your heater?

75w heating ~25G of water. That small of a volume will cool rather rapidly.

I have the 1800w version of that Noma battery back-up and it runs my 800gpm emergency pump for 18-20 hours.