Get your set up on a UPS. The bigger the better. I picked up a CyberPower 1500 unit at CostCo. It run only my tank ( Fluval 206, digital time & light (Finnex Planted+)), the UPS claims 96 minutes of battery run time (under full load). Last power outage which are common in Honolulu lasted about 90 minutes, the tank carried on flawlessly. The UPS handles brown outs equally well.
Cover the tank to prevent heat loss if it's,cold. Get a battery operated air pump, do not feed and run the pump. They are like 15 bucks and some can be setup to systematically come on if the power fails. They will adapt, the lower temps slows their metabolism down so you don't need to feed them and keeps the pollutants down. If your air pump fails use a bucket and just fill and dump back in to oxygenate the water.
Power failures are easy and not really that bad. My tanks lasted over a week during Sandy. Only lost one fish and this was a discus tsnk.
CTAYLOR3737' s suggestion of wrapping the tank is spot on if you've only got one tank and stuff that likes higher temps. Otherwise , don't do anything . I was on generator ( furnace , fridge , microwave only) for 9 days after Sandy . No heat , light , filtration for my 25 tanks . Fed once , no losses , Tank temps. in my lower rack were around 62F.
An easy way to add oxygen to you water is to add a couple drops of hydrogen peroxide every once in a while. It is H2O3 so it disassociates into H2O and oxygen. My friend uses it in his bait buckets to keep live bait alive all day. Works great
A blanket or two, and thats about it to be honest. I also typically just throw the filter pad into the tank to keep everything running. We do have an old UPS that I used for my desktop that still works relatively well, just bulky, that we keep charged and plugged in, right next to the tank. If the power's out for a relatively long time, I can plug in the filter for an hour or so and le the tank get more water movement. Honestly though with the few Battery Operated Air pumps, some air stones, and a blanket or two to keep the tank warm, my fish have all been fine..
Hey raz, I see u live in norcal. Almost all fish will be fine for a few days without a heater with norcal temps even during the winter. So id be more worried like I said about the filter. If there is a black out just put an battery powered air pump in the tank, maybe even an air powered filter if u have one laying around. I would also trow in an air pump in your filter/media to make sure the beneficial bacteria stay alice
I have a battery backup for plugging my filter into, and I've used it a couple of times.
Also, get a battery-powered air pump or two.
As a general rule, fish are fine without light for a while... They'll go all pale, but that's just a reaction to it being dark.
Something not often mentioned when speaking of long term (days? ) power outages is what to do when the power comes back. Too mnay rush to get the temp back to normal but I feel that is a mistake. If the water has gone down slowly and they are fine with adapting slowly to that change, don't rush to get them back to normal temperatures.
We don't rush to throw a bag of new fish into different water so we should not rush to bring them from like 60 back to 75!
If you're using a canister filter and have a long power outage (more than I'd say 8 hours or so), I'd probably unhook and clean the filter to prevent the aerobic bacteria from dying off and polluting the water in the canister - which would then shoot directly into the tank when the power came back on.
Your fish and plants will probably be fine for at least a week, otherwise. Heat tends to be more of a problem then a short cold spell, as long as temps don't get anywhere near freezing. Down here, it's hurricane power outages that are the problem- that's when battery powered airstones and water changes are necessary to keep the temps DOWN and keep the water oxygenated.