An imagined problem and a solution?

Fish need oxygen to breath just as we do and they get it out of the water. The constant pumping of the water out of the tank and through the growbeds and back into the fish tank provides a lot of air to water contact which ensures the continuous exchange of gases.
It suddenly occurred to me a few weeks ago that if I had a pump failure for whatever reason, and I didn't know about it for some time, I only go over to feed the fish once a day, I could possibly end up with dead fish due to low dissolved oxygen in the water.
This is not really likely to be a problem at the moment due to the small size of the fish but when they are bigger it could be a very real problem. I imagine 200 plate sized fish need a fair bit of water/air contact to prevent them suffocating!
So I went looking for a big air pump- just like the ones used in aquarium setups but bigger.
It had to be at least capable of running on 12 volts and even better 12Volts and 240Volts.
I found one on eBay, bid and won, and a few days later it arrived.
I would not want to have it in a home aquarium setup because it is very large and quite noisy compared to normal aquarium pumps.
However it pumps about 40litres of air a minute and the box contains a 12Volt 7Ah sealed lead acid battery and charging circuitry etc which means that if the power fails it continues to run for some hours on battery power alone. I could also hook up a 12Volt input so that even if my inverter fails I can still keep the fish alive.
At least that is the theory!