I wish someone had told me about this when I was a newbie !
IME !
You can also buy these battery backup type "bubblers" in Walmart's camping & fishing dept.
Sold for keeping bait alive during fishing trips.
They come in 3 power output duration's 36 hours, 48 hours, and 72 hours.
The cost is about $8.00 to $22.00 each depending on which power duration you need/choose.
I bought 5 of these 35 hour/$8.00 "bubblers" for 3 tanks. They worked great!
Really handy when transporting purchases, trades, etc. over a long distances.
They use 2 "D" size Batteries, and comes with their own 12" of air tubing, and air stone.
The only draw back with these is...
That they are ONLY good if you're present to turn it on, and place the air stone in the water !
I've found they're Not much good if you're asleep, or away and the power goes off for a long length of time !
So, after more research, I found and invested in the "plug in the wall" type of power pack which has a built in 2 "D" size battery back up.
They sell for about $25.00 each. I think it's a bit expensive But, I've found it was a much better investment !
This one turns on automatically when the electric power goes off !
And then It will automatically run for about 24 hours on battery power until the power comes back on!
Then automatically shuts it's self back off !
Just hide the air stone in your tank, plug it in, and forget it!
Just remember to replace the regular batteries when they are exhausted. (it does not recharge your batteries)
I'd suggest 1 power pack per 25 - 30 gallons of water.
No more getting up in the middle of the night to start battery packs !
No more worry when I'm away from home, or in the hospital, and a power failure happens !
So far! Thumbs up on reliability And, Peace of mind !