An aquarium power outage alarm that reaches you
A power cut stops the filter, the heater, the air pump and the return pump at the same instant. Nothing looks wrong for a while, which is the problem: by the time a tank looks wrong, the damage is done. The useful thing is not a log of what happened — it is being told while you can still do something.
What actually goes wrong, in the order it happens
Most people assume the danger is the tank going cold. Usually it isn't, and the real sequence is worth knowing because it decides what you should do first.
1. Oxygen, within hours
When the filter and air pump stop, so does surface agitation — and surface agitation is where most gas exchange happens. Dissolved oxygen falls, fastest in tanks that are warm, heavily stocked, or both. This is the quickest way to lose fish and the easiest to prevent.
2. The filter bacteria, over hours
The bacteria that convert ammonia live in your filter media and need oxygenated water moving through them. Standing water starves them, and a filter that has sat still for a long stretch can come back with a significant part of its colony dead. The cruel part is the timing: the ammonia spike arrives after the power does, when you think the emergency is over.
3. Temperature, over many hours
Water holds heat well, so a decent-sized tank drops slowly — often only a degree or two over several hours in a heated room. Small tanks, cold rooms and long outages change that, but temperature is generally the problem you have time to think about.
A reef tank is the exception to all of this: corals are less tolerant of falling oxygen, still water and temperature swings than most fish, and the margin is much thinner.
What to do in the first hour
Worth knowing before you need it, because none of it is useful if you are reading it for the first time in the dark.
- Get air moving. A battery-operated air pump and an air stone is the highest-value item in the cupboard. Failing that, gently scooping and pouring water back in from a height agitates the surface and buys time.
- Do not feed. Uneaten food and extra waste is more ammonia in a tank that has lost the ability to process it.
- Keep the filter media wet. If the outage looks long, media sitting in still water inside the canister will fare worse than media in a bucket of tank water with an air stone in it.
- Insulate before you heat. Blankets or a duvet around the tank hold heat far more safely than any improvised heat source, and a large tank loses heat slowly to begin with.
- Leave the lights off. They are the one thing nothing in the tank needs during an outage.
- Test after power returns, not just during. Ammonia and nitrite in the days that follow are the real aftermath of a long outage.
Why you usually find out too late
Every common answer shares one flaw. A tank controller, a smart plug, a Wi-Fi temperature probe — all of them report over the router, and the power cut takes the router out at the same instant it takes out the pumps. The device notices immediately and then has no way to tell anybody. Most surface the event once the power is back, which is a record rather than a warning.
A phone is the exception, for a boring reason: it has its own battery, and with a cheap prepaid data SIM it has its own connection. It can keep talking for hours after everything else in the room has gone quiet.
How OutagePing handles it
Leave any Android phone on a charger near the tank. It watches the charger's power feed rather than the battery level, so it notices within seconds even at 100% charge, and brief flickers are filtered out so a momentary dip does not wake anybody.
- At home: a full-screen siren on that phone, loud enough to wake a room, overriding silent mode and Do Not Disturb.
- Away: with Pro, everyone you have given a code to is woken on their own phone — about three minutes if the monitoring phone has mobile data.
- If the phone itself dies: our servers notice its check-ins have stopped and alert your people anyway, in roughly seventeen minutes. This is the case that matters for a tank in a house nobody is in.
That last point is the one worth dwelling on. A neighbour with a key, holding a code, is a far better outcome for a tank than you finding out at an airport. They need no account and give us no email address — they install the free app and type six digits.
Reptiles, vivariums and incubators
The same alert, a tighter clock. A vivarium holds a fraction of the thermal mass of a tank of water, so ambient and basking temperatures fall quickly once mats and lamps stop. Incubating eggs are less forgiving again. What you do with the warning changes — insulation and a safe heat source rather than aeration — but the problem of not being told is identical, and it is the part that is actually solvable.
What this does not do
It does not keep your tank running: it is an alarm, not a battery. Pair it with a battery air pump and it becomes a plan. It does not send SMS or make phone calls — alerts arrive as push notifications in the app, and by email to anyone else. It is not a certified life-safety system. And the monitoring phone must be Android 8.0 or newer; there is no iPhone version.
Questions keepers ask
How long can an aquarium survive without power?
It depends far more on stocking and tank size than on anything else, but the usual order is: oxygen first, then filter bacteria, then temperature. A heavily stocked or warm tank can be in trouble within a few hours, while a lightly stocked, large, cool tank may be fine for much longer. A reef tank with corals is the least forgiving. The practical answer is that you want to know within minutes, not when you get home.
What actually kills fish during a power cut?
Usually not the cold. When the filter and air pump stop, surface agitation stops, and dissolved oxygen falls — that is the fastest risk in a well-stocked tank. Next is the filter itself: the bacteria that process ammonia need oxygenated flow, and once they start dying the tank can suffer an ammonia spike when power returns. Temperature matters, but a large body of water loses heat slowly.
Will a battery backup air pump be enough?
For many freshwater tanks, a battery air pump running an air stone is the single most effective thing you can add, because it addresses oxygen, which is the fastest problem. It does not keep the filter bacteria alive indefinitely, heat the tank, or run a reef tank's flow. It buys hours, which is exactly what an alert is for.
Can a smart plug tell me my aquarium lost power?
Usually not while it matters. A smart plug reports over your Wi-Fi, and the power cut takes out the router at the same moment. Most surface the event once power returns, which is a log entry rather than a warning. A phone has its own battery and, with a SIM, its own connection.
Does this work for reptile vivariums too?
Yes, and the timing is tighter. A vivarium holds far less thermal mass than a tank of water, so basking and ambient temperatures fall quickly once heat lamps and mats stop. The alert is the same; what you do with it differs, and for reptiles it is usually insulation and a safe heat source rather than aeration.