power outage

You should be ok, 24 hrs. isn't very long. BUT make sure you test the tanks daily for several days and make sure all of the results are still good, doing water changes if necessary

what kind of filters do you have? if that happens again, just take out the filter cartridges or biowheels if you have them, and drop them into the tank to keep them wet.

That is what I would do. The flow from the battery operated pump should help keep things going if they are in the tank.

In the event of an outage, if you were home would it be any benefit at all( regarding keeping the bacteria alive) to siphon some tank water into the filters every couple hours?

I'd be most concerned about canister filters, especially if their media were not clean. A really dirty canister could get pretty nasty in 24 hours... I don't know if they can go anoxic that quickly and start producing hygdrogen sulfide, but I bet they could start to get stinky. A cleaner canister would almost certainly be OK. I've had some that were off over a weekend (power outage at work), that came back on before I even new they had been off. No problems.

HOB and other filters that have exposure of the media trays/wells to air should be OK, although occasionally aerating the water around the media would probably help the bacteria. My guess is that wouldn't really be necessary though, at least not for a 24 hour outage.

Jim