The UPS---just get a big unit and minimize what stays running: a small pump for bubbling is A number 1. Heater won't be a problem and they're the most power hungry. You're probably already above 80 down there...maybe a small chiller with a reliable thermostat might be in order: I'm not sure of their power draw. Lights on timer, NOT connected to UPS. Consult a knowledgeable computer store (triple underline knowledgeable) and read how much wattage over how much time on the UPS label before you buy. They vary widely. Most importantly, a friend with a key who'll show up and check after power comes on again.
Your timers will of course be screwed and will have to be reset, or your critters can just get used to sunlight at 2am: they don't really care. If heat is a serious issue, you might even deliberately reverse day and dark to get the lights in the coolth (relative) of the night.