Having a backup system is very handy, bordering on essential. If and when the power goes out, you want to be sure that your fish are not going to die. A well stocked system filled with fish will not last long as they consume the available dissolved oxygen within the water, so you need a way to get oxygen into the water that doesn’t rely on mains power. There are a few ways you can go about this, you can keep battery operated aerators or a generator handy for when the power goes out so that you can implement your contingency plan when things go wrong. But, generally as Murphy’s law would have it, if the power is going to go out, it will be when you are not home, so you will be unable to react to the power failure.
An AC/DC Air pump with internal battery
This means you will need to have your backup system already thought out before hand, and it will need to be automatic. There are a couple of simple ways you can do this. We like to use AC/DC aerators, these are air pumps with internal rechargeable batteries in them. Normally they run while plugged into the power, pumping air through air lines and air stones in the fish tank. When the power goes out they switch automatically over to their internal batteries and continue to pump air into the water keeping the fish alive for the life of the battery within the unit, often up to 10 hours. When the power comes back on, the internal battery is recharged. Another method used by some is to make their own back up using either water pumps or air pumps, using batteries, something like a car battery, an inverter, a trickle battery charger and a power fail switch. Essentially this does the same thing as the AC/DC air pump above, but it’s larger and in an individual components form. This type of system can be chopped and changed, you can leave out the inverter and use 12/24V DC components if they are readily available. There’s a lot more information about backup systems on the Backyard Aquaponics forum.