Pondmaster ap 100 and ap 60. Cheap. Moves tons of air. Negatives are they're Loud and the diaphragm blows every 3-6 months.
One thing that's saved me 5 figure losses are having extra compressed oxygen tanks hooked to regulators. I use my old CO2 hydroponic atmospheric regulators. Cheap at indoor gardening store or online. The regulators lead to hose line that T's and splits to multiple airstones which sit in every tank system. We have a lot of storms on the edge of the rainforest so if the power goes out all we have to do is crack the valve on the O2 cylinder and every tank instantly has aeration. 55lb cylinder can last for days on multiple systems. I keep a cylinder of varying size in each fish room ready to go. This is in addition to the airpumps running 247 as a backup.
I have backup propane generators built into our house that my neighbors are trained to start in our absence. But the air tanks are a great backup, instant aeration.