For my system I power my controller and one of my pumps with this ~300WHr power station - which will
power both for days:
It's not available now, but it worked great for my purpose with one 12V out that I could use for the controller and one 24V that I used for my circulation pump:
I opted not to use a UPS for a couple of reasons:
UPS are typically spec'd for the peak wattage they can deliver - something on the order of 500-1500W - which they can do for only a few minutes. Based on the runtime calcs, I'd estimate the actual battery capacity to be on the order of 30-100Whrs - meaningfully lower than a batter backup I could get for the same price. The physical size of the UPSs I was looking at are also much larger and I was trying to make a pretty compact system. Lastly, there are losses associated with converting back and forth from AC to DC so I reasoned that for the same size battery I could ultimately get more run time with a direct DC connection to the battery.
There are certainly some caveats to using a backup like mine. For one, very few have a 24V out, so it's hard to find one with good reviews that will work for this purpose. Also many don't allow simultaneous charging and power draw needed for this application. Additionally, the polarity of the output on the 24V and 12V connections is not obviously listed for most products so you'll need to manually check this to confirm it isn't wired backwards - fortunately it seems most products in this voltage range are center positive but it isn't a guarantee. Lastly - while this has worked great for me, it isn't really the intended application and I would expect an actual UPS is more reliable.