as long as you've been doin regular water changes then an hour and half with no oxygen is still manageable but if the power outages becomes very frequent you should get atleast a battery aerator pump for support while a stand-by generator will be the best.
i had an 8 hour outage at 3 degrees F ouside and mine was fine, I worried a lot, he never even started to breathe thru his mouth, I got a generator though, scared me.
I use computer UPS' and a small air pump split between every couple of tanks (check valves, check valves, check valves ! ). Had a homemade 12vdc generator w/ converter, let someone borrow it and somehow it got fried AND they ruined the engine trying to rev it higher to get voltage out of it ( of course it wasn't their fault ! ) ( never a borrower or lender be... I always wondered what my mother ment by that when I was little) so have to start over on that one.
If we could teach the fish to pull a leash then hook it to a wheel and have them swim in a circle to turn a little generator ( kind of a mouse in a exercise wheel thingie )
The problem with power outages is that within 2 to 4 hours, the bacterial bed in your canister filter becomes partially or totally anaerobic. Anaerobic filters produce very noxious (and toxic) by-products, which could hurt or kill your tank's inhabitants. A UPS (uninterruptible power supply) is a worthwhile investments for those who live in areas that are prone to power outages.
theyre really primitive fishes and they can gulp air from the surface of the water if they feel they need too. but thats not a good sign and only means the water quality is not that optimum. though ive experienced power outages here up to 8 hours and my aro is stil doing okay. the best way to prepare for this is to have good water quality ALL THE TIME