Life at the Bottom Changes the Risk
A power cut reaches a corydoras differently from a surface fish. Corydoras live on the substrate, sifting sand through sensitive barbels in a group, and the water down there is the first to lose oxygen and the first to collect settling waste when filtration and circulation stop. They do have a famous backup: corydoras can gulp air at the surface and use it internally, which is why an established group often cruises through a short outage calmly. That trick buys time rather than immunity, and a long, warm, still outage still turns the bottom layer into the least hospitable part of the tank.
Keep Air Moving Without Churning the Tank
If you own a battery air pump, run an air stone so its rising bubbles drag bottom water upward and break the surface film; position it so the school can rest away from the strongest current when it wants to. Without a pump, disturb the surface gently at intervals with a clean jug, pouring tank water back from a small height, and watch the corydoras respond: relaxed foraging and occasional unhurried trips to the surface are reassuring, while constant frantic darting upward is not. Keep the lid mostly closed between those checks to hold warmth in a heated tank, and wrap the glass in towels if the room is cold, leaving the fish in dim light to rest.
Stop Feeding and Protect the Filter
Do not feed the group during the outage, however pleading the whiskered faces at the glass look. Sinking wafers and pellets land exactly where oxygen is scarcest and decay exactly where the fish breathe and feed, so one well-meant meal can do more harm than a day of hunger. Leave the filter media submerged and the unit ready to restart on its own. Avoid a mid-outage water change unless the water was already in poor shape before the cut; a corydoras tank at a slowly drifting temperature is safer than one shocked by unmatched replacement water carried in by torchlight.
Restart, Test and Watch the Barbels
When power returns, check the heater is working, the filter is primed and flowing, and the temperature is settling rather than swinging, then wait before offering a small sinking meal you watch them finish. Test for ammonia across the following days, because a long outage can thin filter bacteria, and change modest amounts of conditioned water matched for temperature if readings rise. Inspect barbels and bellies as the group resumes sifting: erosion, redness or a fish isolating itself under decor after an outage deserves attention, since bottom fish meet the worst of any waste spike first and show it on the skin that touches the substrate.
Share the Outage Jobs Before the Next One
A cut handled by one tired person at midnight is where steps get skipped, so decide in advance who insulates the tank, who runs the air pump, who checks the school and who handles the restart and testing. Note the lowest temperature and the outage length while you remember them, because that record explains any illness that surfaces days later better than a guess will. If several corydoras keep gasping, lose balance or stop feeding after warmth, flow and clean readings are restored, seek an aquatic veterinarian's advice promptly. Setting those jobs out in KinsLe's Care Teams gives each helper a named outage task for the tank, marked complete with a timestamp as it is done.