Inverter for power outage

[mrbacony]

I am looking at buying an inverter to use for my powerhead if the power ever goes out. I have a 50mah marine battery i keep charged all the time and figure I could hook up the inverter to this to power the pump.
Does anyone have advice as to the wattage on the inverter I should get and how long the marine battery would power a powerhead in the event of an outage. I have a 530 gph Sicce and according to the website only pulls .05 amps.

 

[Daddy-o]

I bought a couple of these for emergency. They hook right to 12 volt

[Hot Item] Baitwell Pump 12V Livewell Pump for Fishing

Flow Rate: 600gph Rated Current: 1A Certification: Ce, ISO9001:2008 Voltage: 12 V DC/24V DC Protection: Anti-Airlock, Ignition Protected Outlet Dimension: 19mm/3/4''

cnseaflo.en.made-in-china.com