Keeping Aquariums, Reef Tanks & Reptiles Alive in a Power Outage

In a freshwater tank, do nothing but keep the lid closed for the first hour or two; in a longer outage, falling oxygen is a bigger threat than the thermometer. In a reef tank, power water movement at the surface first. For a reptile, no vet source publishes a safe number of hours without heat, so act on room temperature and symptoms: a body temperature approaching 32°F, or any hypothermia sign, is a vet emergency. A dog or cat can usually ride out an outage on blankets and body heat. A 40-gallon reef tank or a bearded dragon’s basking lamp cannot.

The American Red Cross’s own pet-disaster guidance is dog-and-cat focused, and explicitly refers reptile and exotic-pet owners elsewhere for species-specific guidance. This page fills that gap. Symptoms override clocks, and any figure that is not clinical is labeled as such.

Do This First: The Outage Just Started

• Don’t feed fish or reptiles. Digestion consumes oxygen fish can’t spare in a tank about to lose aeration, per NC State veterinary aquatic medicine faculty. A reptile’s food can’t be properly digested at a lowered body temperature and risks bacterial overgrowth.
• Disable auto-feeders so uneaten food doesn’t foul the water, and keep the lid closed. Move the tank away from drafty windows or doors only if you can do it without jostling it.
• Check what has actually failed. A dead heater in a warm room is a different problem than in a cold house in January.
• Don’t open the enclosure repeatedly to check; every lifted lid or screen top lets out heat.

For the first 1 to 2 hours in a freshwater tank, Aquarium Co-Op’s guidance is to do nothing else; saltwater and reef systems go to the reef section. NC State’s Gregory Lewbart says tropical and temperate fish tolerate the high 80s or low 90s°F “for a day or more”, and most tropical fish tolerate the low 60s or even high 50s°F “for several hours”. You have longer on the warm side than the cold side.

Freshwater Tanks: A Staged Timeline

This combines NC State’s veterinary guidance and Aquarium Co-Op’s staged plan. It is not a lab-tested countdown, and every row is for freshwater.

Time since power loss	What to do	Source
0–2 hours	Nothing. No feeding, no extra aeration, no water changes.	Aquarium Co-Op
2–8 hours	Monitor water temperature if you have a battery thermometer. Keep the lid closed.	Aquarium Co-Op
8 hours+	Run supplemental aeration (battery air pump, or manual agitation with a cup) for about 1 hour, then repeat roughly every 8 hours; closer to every 4 in heavily stocked tanks.	Aquarium Co-Op
Any point	If ammonia tests above 1 ppm, do a 10–30% water change.	NC State (Gregory Lewbart)
After power returns	Withhold feeding for 24 hours so biofiltration can catch up.	Aquarium Co-Op

Aquarium Co-Op’s own exception outranks its intervals: if you notice your fish gasping for air, you may need to add oxygen earlier and more often. In a longer outage, falling oxygen is a bigger threat than the thermometer.

What Moves Your Clock

No source publishes a formula, only directions. More water buys more time (“greater volumes of water do not change temperature as easily”, per Aquarium Co-Op). A heavier stock load spends oxygen faster, which is why Aquarium Co-Op shortens the aeration interval to 4 hours. NC State’s intervention line for tropical fish is “Once temperatures dip to the mid-50s”. Insulation (a blanket, sleeping bag or newspapers, in layers) slows loss and never adds heat. NC State also caps how fast to correct a chilled tank: “A 10 percent water temperature change every hour or two should not endanger fish.” Pouring hot water into a cold tank to catch up is its own injury.

Measure Your Tank’s Own Cooling Rate

Record water temperature and the time, repeat an hour later, and subtract to get degrees per hour; divide the gap to your line by that rate. For tropical fish the line is the mid-50s; temperate species such as goldfish or koi, NC State says, “should be fine without changing the environment.” In a summer outage the ceiling replaces the floor: the high 80s or low 90s°F. Purely as arithmetic: 74°F then 72°F an hour later is 2°F an hour, and the roughly 17°F gap to the mid-50s gives about eight hours. NC State’s tolerance for the low 60s and high 50s runs “for several hours”, not indefinitely, so read the result as the latest hour you can act. Stock load moves oxygen, not temperature, so gasping fish remain your oxygen clock. For reptiles, divide toward your own species’ published minimum.

When the Timer Runs Out: NC State’s Options in Order

NC State lists ways to “elevate the temperature” and labels its last item “An absolute last resort”. Six apply to an indoor tank; reading the order as an escalation is this page’s note.

1. Restore power to your own equipment with a generator or an extension cord to a working outlet.
2. A safe external heat source. NC State names propane or kerosene heaters; the key word is “safe”. This page does not recommend burning fuel indoors, because of the carbon monoxide risk below. See outage improvisations that endanger pets.
3. Move the fish to a warmer place; NC State says heavy-duty zip-top bags work well.
4. Move the aquarium, “an option, though challenging”: up to 70 percent of the water may be discarded (a gallon weighs 8 pounds).
5. If the fish can’t be moved, warm the water slowly with warm dechlorinated water, inside the 10 percent ceiling.
6. Last: don’t pool systems. Mixing fish from different tanks greatly increases the risk of spreading viral, bacterial, fungal and parasitic disease.

In a summer outage, clear the water surface to increase gas exchange and stir the water to raise oxygen. To catch fish, herd them into a bag with a net; lifting with the net alone can damage the protective mucus layer.

Heat Packs and Evacuating Fish

If the room is cold, a chemical heat pack taped to the outside of the tank, never in the water, can slow heat loss. Aquarium Co-Op’s rule of thumb is one pack per 20 to 30 gallons; that is retailer guidance, not a tested figure, so settle the count on your thermometer and see the heat pack limits below.

If you must leave and cannot take the tank, NC State’s transport guidance says fish packed sparsely (about 5 inches of fish per gallon) in a bag of roughly 1/3 water and 2/3 air can survive at least 36 hours if the outside temperature stays adequate. See evacuating fish during a hurricane.

Reef and Saltwater Tanks: What to Power First

A reef system fails faster than a freshwater tank because the return pump, powerheads, skimmer and often the auto top-off all stop at once, on top of the heater. Bulk Reef Supply says that without water movement “dissolved oxygen levels will drop rapidly, especially in tanks with a higher bioload.” The freshwater do-nothing opening is not the answer for a reef.

If you can only power one thing, power water movement at the surface. The evidence points there from several directions, though no source states a consensus ranking:

• AZA: an inability to maintain adequate water flow, oxygen, temperature and gas saturation can result in catastrophic illness or death among tank occupants. Lighting is not on that list, but AZA does not rank the four or call lighting unimportant.
• Bulk Reef Supply, under its uninterruptible-power-supply heading: “Prioritize running powerheads or air pumps to maintain oxygenation.”
• Reef Builders’ Jeff Kurtz puts temperature control and aeration or circulation ahead of lighting, and says reef lighting draws so much power that on a limited backup it will likely be impractical.
• NC State calls lighting “the least of your worries” for fish but adds that tropical reef aquariums with live sponges and coral are more of a concern. Its figures are about fish, so none are carried to corals.

The best-credentialed sources name light and decline to rank it. Public aquarium curator Jay Hemdal lists oxygen, light for corals, temperature and, in long emergencies, nitrogenous wastes, in no order. Extension veterinarian Roy Yanong told Florida Sea Grant that reef tanks need extra care and ideally a generator, since more oxygen and lighting is needed. So flow first is a judgment about scarcity, not a claim that darkness is free.

Oxygen in Hours, Darkness in Days

Two papers that never cite each other explain the order; joining them is this site’s own step.

Oxygen runs in hours to a day. Johnson and colleagues (Scientific Reports, 2021) held two Caribbean coral species at four oxygen levels. At about 1.0 milligram per litre, Acropora cervicornis suffered tissue loss and death within a day, while Orbicella faveolata was unaffected after 11 days of continuous exposure. These are concentrations under controlled bubbling, not time with a pump off, so no one can convert them into hours for your tank.

Darkness runs in days to weeks. Bessell-Browne and colleagues (Scientific Reports, 2017) held corals under six light levels for 30 days, the lowest near total darkness. Corals at the lowest light were bone white by day 20, and the authors say corals “began noticeably paling after 4–5 days and were heavily bleached after 10 days”, so plan against the shorter. Acropora millepora showed no tissue loss at any light level over the 30 days, while Pocillopora acuta suffered partial mortality. In one earlier study the paper compiles, three of four species were alive after 60 days in darkness: bleaching is not death.

The corals were unfed laboratory animals, and each experiment kept the other variable normal. That is why the pair argues for the pump: a month of near darkness in one species versus about a day of severe oxygen depletion in another. In an outage lights and pumps stop together, so this page’s reading is that flow matters most in the dark.

How Many Hours Do I Have?

No source publishes an agreed number, and those who give one count different events. Reef Builders’ Shane Coleman says “at least 2-3 hours” before livestock can even start to show stress; Hemdal says low dissolved oxygen develops within a few hours; CoralVue, which sells battery backups, says fish and corals can perish in as little as 4 hours without flow. Those are stress, low oxygen and death.

The days figures assume the pump runs. Bulk Reef Supply says a tank “should survive for 2-3 days without the filtration, heater, or lighting so long as you have a powerhead moving the water”. Yanong says the first day or two should be stable “especially with proper aeration” for a prepared tank you are not feeding. The home answer is an alarm: Bulk Reef Supply advises power monitoring that messages your phone when the tank loses power.

Watch the animals. Hemdal says to begin emergency aeration once “a slight rise in their breathing rate” is noted. His logic is about stretching a finite supply such as ice or a battery you cannot recharge; it is not a grace period for the first pump, and it does not apply to a backup that starts itself. Start the water moving, and use breathing rate to decide when to spend what you cannot get back. Yanong lists fish gasping at the surface among distress signs: “If you notice these signs, seek advice from a veterinarian or an experienced aquarium expert.” Find that number before the power goes out.

The Order Under Scarcity

This ordering is this page’s judgment, built on the sources above.

1. Water movement at the surface. A circulation pump moves more water; an air pump uses less power and most start themselves. With nothing to plug in, Bulk Reef Supply says to “manually stir the water every hour”, and Coleman describes pouring sump water back into the display from a height, almost continuously. The intervals disagree and none is sourced; aim for a moving, choppy surface.
2. Temperature, only if you can carry the load. A reef heater draws hundreds of watts, against a 20 watt pump in CoralVue’s example. Coleman says hotter water is more dangerous because it holds less oxygen, so heating is usually the load to drop unless you live in a very cold climate. In summer, NC State says to remove anything from the water’s surface to increase gas exchange and to minimize direct sunlight if the water gets too warm. This page gives no reef cooling rate.
3. Filtration and the skimmer. Bulk Reef Supply says waste accumulates quickly, a slower clock than gas exchange. This page gives no reef ammonia threshold or water-change figure, because the published figures are for freshwater ornamental systems.
4. Light, last. Kurtz says most corals can easily tolerate a few days of reduced light or darkness. Bulk Reef Supply says prolonged darkness can stress corals, and Hemdal says that in a long outage corals begin to die from lack of light or some other factor. If the outage runs to days, the problem becomes a bigger supply or a different plan. See the weeks-long outage plan.

Don’t split a small supply across several loads: one pump run properly beats a pump too slow to break the surface, a heater too brief to hold temperature and a light nobody needed. EcoTech’s manual says two pumps on one backup cut each pump’s runtime by about half.

Reef Heaters: Why Battery Backup Is Mostly a Myth

Aqueon suggests 5 watts per gallon for tanks of 55 gallons or less and 3 watts per gallon above 60 gallons, plus a larger or second heater in an especially cold room. Reef keepers broadly hold 76 to 80°F and treat roughly 83 to 84°F as the upper edge, which is consensus, not a published coral death table. Bulk Reef Supply: “Even slight fluctuations can stress or kill sensitive reef life.”

A backup air pump draws under 2 watts and can run a day or two on D cells. A reef heater, typically 100 to 200 watts at Aqueon’s 5 watts per gallon for a 20 to 40 gallon tank, is another order of magnitude, so backup means a portable power station or generator that buys hours, not days. The realistic plan, per Bulk Reef Supply, is insulation plus sealed warm-water bottles floated in the tank, or frozen ones if the risk is overheating.

Pump Placement and Water Level

EcoTech’s manual recommends placing a pump on battery backup as high in the tank as possible to disrupt the surface and improve oxygen diffusion. Yanong says good aeration shows as a turbulent, “choppy” surface. Evaporation continues while the auto top-off pump is off, so a pump set at the old waterline can end up drawing air or running dry. That caution is this page’s. Set the pump high, check the water level every few hours, and lower the pump if it falls. When power returns, top off gradually with fresh RO/DI water, not more saltwater, and re-check salinity with a refractometer.

Battery Backup Runtime for Reef Pumps

A direct-current pump on a matched battery is the one case where manufacturers publish hours, because no inverter is in the path. EcoTech’s Battery Backup manual (document code 041713) prints hours for one unit and two units: MP10 at 72 and 36, MP40 at 36 and 18, MP60 at 20 and 10, with the footnote “*Actual hours may vary due to operating conditions and battery cycle times.” Units means pumps, not batteries; two backups daisy-chained double one pump’s runtime. As of August 19, 2026, EcoTech’s store lists the product as compatible with all VorTech and Vectra generations (Vectra needs a separate booster) with no runtime. The warranty says a pump on battery backup “may not produce enough flow to prevent the death of aquarium livestock.” EcoTech recommends a monthly test: unplug both the backup and the pump and read the charge on the pump controller.

CoralVue’s IceCap Battery Backup v3.0 (2.5 Ah) gives a formula, (mAh × volts) ÷ (watts × 1000) = hours: 12.5 hours for a 0.2 amp pump, 1.5 hours for a 20 watt pump at 12 volts. The page says 12V twice and 24V once, which doubles or halves every result, so ask CoralVue which applies. It is “NOT compatible with Reef Octopus VarioS Pumps, EcoTech pumps, Tunze, Jebao, or AI Nero pumps”, and a backup that does not drive your pump is not a backup. Treat any quotient as a ceiling; see the pet load power budget calculator.

Car Battery and Inverter: The Hazard Nobody Attaches

Reef Builders suggests a 12-volt car battery and inverter with no safety note. Hemdal says to keep expected wattage under 80% of the inverter’s continuous rating and not to use one rated above 300 watts on a cigarette lighter socket, which may blow the vehicle’s fuse. OSHA’s construction standard (29 CFR 1926.441) requires that “Batteries of the unsealed type” be vented so gases do not form an explosive mixture. It is a workplace rule, not a household one, but it names the hazard. This page’s own position: keep any battery out from under the tank and away from every water path, and prefer a purpose-built aquarium backup or listed power station over a loose car battery indoors. Neither EcoTech nor CoralVue states a sealed or unsealed designation, so find out which kind you hold.

What This Page Does Not Tell You

• No hydrogen peroxide oxygenation. Hemdal says it is “difficult, if not impossible to dose correctly during an emergency.”
• No ammonia neutralizer dose. Yanong says conditioners “may reduce ammonia’s harm but doesn’t remove it.” Ask a veterinarian or reef specialist what to add.
• No pressurized-gas improvisation such as the SCUBA-cylinder aeration Hemdal describes.
• No photoperiod ramp for restarting reef lights. No source publishes one; ask a reef specialist or your lighting maker.

Battery Air Pumps: What Is Published

A battery pump aerates automatically instead of you setting an alarm every 4 to 8 hours. Stage it ahead: after a no-warning event like an earthquake or tornado there is no shopping window. The pumps work in saltwater too, where airflow matters more because the bioload competing for oxygen is higher.

Pump	Battery	Runtime (published)	Tank capacity	Source
Aquarium Co-Op Battery Backup	Rechargeable lithium-ion	20 hrs continuous / up to 40 hrs power-save	Not published	aquariumcoop.com
Penn-Plax Silent-Air B11	2x D	72 hrs or more per Penn-Plax (SAB11); up to 48 hrs per the retail listing	Up to 29 gal	Penn-Plax; Amazon listing (48 hrs)
Penn-Plax Air Pod (APB1)	4x D	Up to 150 hrs (retail listing only; not published by Penn-Plax)	Up to 55 gal	Penn-Plax (battery, capacity); Amazon listing (runtime)
Aquatop BREZA AC-DC-ONE	2x D	No published spec	Not published	aquatop.com

The Air Pod’s 150 hours is a retail-listing number; Penn-Plax’s page publishes the battery count, capacity and switchover but no runtime. For the B11, Penn-Plax’s own SKU (SAB11) page says that depending on the batteries it “can provide your fish with an uninterrupted supply of oxygen for 72 hours or more”, longer than the listing’s 48. Provision against 48 and stage fresh D cells. The Aquatop has the highest airflow (2.5 L/min) but no published runtime, and the Aquarium Co-Op unit recharges, so it wins over many outages if you keep it charged. An air pump handles oxygen only; a power station can run a 100 to 200 watt heater for hours, not days; moving the animal solves both. See quiet generator versus portable power station.

Reptiles: Why There Is No Single Safe-Hours Number

No vet-school or peer-reviewed source publishes one figure for reptiles as a group; tolerance varies by species, size and room temperature.

• Bearded dragons: VCA and Merck publish no hours-without-heat figure, and no vet-school or university herpetology source does either. Normal husbandry keeps the cool zone at 75 to 80°F and the basking zone at 90 to 100°F, per VCA. Treat a room sliding toward the cool-zone floor, or any hypothermia sign, as the point to act.
• Reptiles broadly: brumation-level cold can be tolerated for “a few days” short term, but prolonged cold raises real illness risk, per Dr. Laurie Hess, DVM.

The snake and gecko figures in the table below come from keeper care guides, not clinical sources, so treat them as consensus. Don’t average any of these, and don’t read the missing bearded-dragon figure as license to wait. The vet-emergency rule below overrides every row.

Species	Normal husbandry temp	Emergency room-temp floor	Rough tolerance without heat	Source (authority tier)
Bearded dragon	Cool zone 75–80°F, basking 90–100°F	No published figure	No published figure; watch the habitat and the animal	VCA (husbandry range only)
Ball python	Basking 88–92°F, warm side 80–85°F, cool side 76–80°F	Ambient above ~55°F	~6–12 hrs; sustained below ~72°F risks digestive shutdown	ExoPetGuides / Regarding Reptiles (care-guide consensus)
Leopard gecko	Warm/belly 88–92°F, cool side 73–76°F, night floor ~68°F	Room above ~60°F	A few days if the room stays above 60°F; first ~12 hrs uneventful	Reptile Craze (care-guide consensus)
Other snakes (general)	Species-dependent; mid-70s°F typical at night	Ambient above ~55°F	~6–12 hrs; cold-sensitive boas and pythons fare worse	Keeper consensus

The Vet-Emergency Threshold

This is the one number here with a clear clinical source. PetMD (Sean Perry, DVM): “The closer the reptile’s body temperature is to freezing (32 degrees F) the more of a medical emergency it will be.” A body temperature approaching 32°F, or any hypothermia sign PetMD lists, needs a vet now. The signs are lethargy, decreased activity, decreased appetite, increased sleeping, poor growth rate, decreased defecation or urination, secondary infections, and death. Chronic cold also suppresses immune function, which PetMD says can cause life-threatening infections even after the hypothermia is corrected, so “he warmed back up and seems fine” is not the end if exposure was prolonged. An animal you cannot rouse is also an emergency; that is common sense, not part of PetMD’s list.

Never attempt rapid re-warming. PetMD says warming a hypothermic reptile too fast can cause life-threatening complications. Gradual, temperature-controlled rewarming and a vet call is the response, not a heat lamp at maximum.

Keeping Reptiles Warm Without Grid Power

• Insulate first. Towels, blankets, or moving a smaller enclosure to an interior room away from exterior walls and drafts costs nothing.
• Heat packs, with a barrier. See the next section.
• SnuggleSafe pads, once you can charge one. The maker rates it for up to 10 hours per microwave charge, so it helps once a generator runs or grid power returns. It is marketed for cats, dogs, rabbits and small animals, not reptiles; treat it as a bridge.
• Never use a human hand warmer. The prohibition is unconditional, for two reasons. Burns: HotHands publishes an average of 135°F and a maximum of 158°F for up to 10 hours, built for a human palm through a glove. Oxygen: these warmers heat by iron oxidation and consume oxygen, a problem in a closed enclosure. An unsealed enclosure removes the second reason and leaves the first, so the rule is to keep it off the animal, not just out of a sealed container.
• Keep exotic pets away from combustion fumes. If you improvise warmth with candles or a propane heater, keep the reptile or aquarium room clear of the fumes, per Dr. Laurie Hess, DVM.
• ASPCA kit guidance: pack a sized soaking bowl and a heating pad or other warming device ahead of time.

Hedgehogs depend on heat the same way; our hedgehog emergency preparedness kit covers the no-power backup heat source and the temperature line that means it is time to act.

Heat Packs in a Reptile Enclosure: What the Rated Hours Mean

The rated hours describe a chemical reaction in a sealed pouch. Every published temperature figure is for a closed insulated box of about one cubic foot, and no manufacturer, reseller or veterinary source converts a rating into usable warmth for a terrarium.

The rating belongs to the pack. UniHeat USA says oxygen starts a controlled oxidation of iron powder in the pouch that releases heat over the rated duration, and it names seven durations from 20 to 120 hours; plan around the one printed on your packet. UniHeat Canada’s sizing advice is about days in transit, not the container.

A terrarium is not a shipping box. UniHeat USA says a single 72-hour pack holds an average internal temperature of approximately 70°F inside a standard insulated 1 cubic foot shipping box. UniHeat Canada says a warmer in an open room is in too large an open-air environment to warm up properly. A 4 by 2 by 2 foot enclosure is sixteen cubic feet, often with a screen top. UniHeat’s FAQ says “DO NOT place shipping warmer directly on or beside sensitive living things, as they may be harmed”, says warmers are not guaranteed to keep animals alive in extreme cold, and advises: “It is always best to run some trial-and-error tests before hand.”

The publishers disagree about one pack. As of August 15, 2026, Pangea Reptile gives the surface temperature of UniHeat’s 40-hour pack as about 110°F at peak, and a reseller, SaltwaterAquarium.com, as an average of 100°F. UniHeat’s own 40-hour chart, labeled surface temperature, peaks just under its 150°F gridline (gridlines are 30°F apart, so approximate). If you planned around 110°F and the chart is right, you planned about 40 degrees low on a surface near an animal. Peak times range from 30 to 40 minutes (UniHeat USA) to 17 to 19 hours (Pangea), so activate a pack early and confirm with a thermometer. On a second pack, Pangea says each extra pack adds about 10 degrees in a 1 cubic foot box, UniHeat Canada says 5 degrees, and UniHeat USA says to use only one per shipment, so this page gives no packs-per-enclosure figure.

What stops a pack. Pangea says that if the box falls below 32°F the pack “may stop working because the water in the heat pack may freeze.” SaltwaterAquarium.com agrees, and UniHeat lists its 40-hour pack as “Best above 35°F ambient conditions”. Neither gives a recovery time, so a long winter outage in an unheated space is where these packs are least reliable. UniHeat Canada says a pack that arrives frozen should not be opened until it has warmed up for several hours. A pack also fails if sealed in an airtight container (the reaction needs oxygen), if its red-striped vents are covered, or if it gets wet (UniHeat says water permanently deactivates it).

Burns. Merck’s standard is that heaters “should be thermostat controlled, screened from the animals, and positioned toward one end of the enclosure to provide a thermal gradient.” A pack has no control loop, so it fails the first requirement; screening and a gradient are on you. PetMD says reptiles “fail to readily withdraw from heating sources that are dangerously hot”, and a thermal injury can take a few days to fully set in, so there may be no sign at the moment. Its burn signs run from reddened skin and blisters, through a hunched posture, squinting and decreased appetite, to charred or blackened skin and deep wounds. A suspected burn is a vet visit; this page gives no treatment.

No manufacturer says a pack should touch an animal. SnuggleSafe’s sheet says: “A SnuggleSafe heatpad must never come into direct contact with an animal”, not to use it with an animal that is unconscious or cannot react to thermal discomfort, and gives a surface temperature of about 65°C (149°F) just out of the microwave. Joining that exclusion with PetMD’s finding is this site’s own reasoning: a reptile is functionally the animal the exclusion describes, all the time. A barrier is the whole safety mechanism, and with published surface figures running from about 100°F to near 150°F, design for the top.

Stocking rule and advance test. The stocking rule is this site’s own: divide the hours you expect without normal heat by the pack’s rated hours and round up, and run the packs one after another, never together. It is a number for a drawer, not a promise about an animal. Test one pack in your own enclosure on a normal day: UniHeat describes wrapping an opened pack in a cloth bath towel in a room at 65 to 70°F and waiting “at least 30-60 minutes.” Put a thermometer where the animal sits, with the enclosure empty or the animal in a separate secure container, because a reptile will not reliably move off a surface that is too hot and a burn can take days to show. Ask your veterinarian in advance which temperature range and warning signs fit your animal.

When Cold Is Not the Failure Mode

For part of this category, the warming advice above would be the injury.

Cool-water species. The University of Kentucky’s Ambystoma Genetic Stock Center, which maintains the reference axolotl colony, holds its animals at 15 to 17 degrees Celsius, roughly 59 to 63°F, using building HVAC plus two 6-ton auxiliary air-cooling units. For these animals the emergency is the summer outage that stops a chiller or air conditioning; Merck says water chillers and air conditioning have to be considered for amphibian enclosures. No clinical upper-lethal figure is published here, so check your animal’s husbandry source and ignore this page’s warming steps for it.

Humidity. An outage takes out misters, foggers and humidifiers along with heat. Merck says “Humidity that is too high or too low can create serious problems”, including shedding failure, and that amphibians need moisture to prevent desiccation. Covering an enclosure holds humidity as well as heat.

When to Relocate the Animal

Insulation and heat packs buy time but do not fix a house that loses heat for days. Move fish or reptiles to a neighbor’s powered home, a shelter with exotic-animal capacity, or a running vehicle as a short bridge when:

• heat packs or battery pump are running low and cannot be replaced or recharged;
• a reptile shows any hypothermia symptom (symptoms override the clock);
• the outage outlasts your gear’s published runtime (72 hours of UniHeat with no restoration timeline, for example);
• room temperature is dropping toward the low 50s°F or below for reptiles, or toward the high 50s°F for fish, with no sign of stabilizing.

If the Warm Place Is a Running Vehicle

A car is the warm space most people reach for at 2am, and the only option here that can kill the person carrying the animal to it.

• Never run the engine in a garage; an open door does not fix it. The EPA says “DON’T idle the car in a garage” even with the outside door open, because fumes build up very quickly in the garage and living area. Back the vehicle fully out first.
• Clear the tailpipe and crack a window. The National Weather Service says “Clear snow from the exhaust pipe to avoid gas poisoning” and to “open the window a little for fresh air to avoid carbon monoxide poisoning.”
• A low enclosure is no safer. The ASPCA lists vehicle exhaust among pet carbon monoxide sources, gives the rule “Never run engines in a closed area”, and notes the gas is roughly the density of room air. Birds are more sensitive still.
• A bridge, never a place to leave the animal. An unattended car swings from too cold to too hot with nobody watching.

See our blizzard stranded-car guide for engine cycling and our generator carbon monoxide guide for the same mechanics with a generator.

After the Power Comes Back: Confirm Every Load Restarted

The lights come on and the heater stays dark, because the switch it was plugged into came back off. It is usually a documented smart-plug setting, named differently by brand.

Brand line	Setting	What the manufacturer documents
SONOFF, through eWeLink	Power-on state	ON, OFF, or KEEP (state before the cut). ITEAD’s support article names the default as OFF.
TP-Link Tapo	Default State	Last On State, On, or Off, per device; TP-Link says to update the plug and app first.
Meross	None named in the public FAQ	Devices retain settings and reconnect after power returns, which is not the same as energizing a socket.

• Set it to ON, not last state. A thermostat-controlled heater cycles off by design, so last state is a coin flip on exactly the load you cannot lose.
• Test it. Pull the plug at the wall, wait a minute, plug it back in and see whether the load energizes without an app. Repeat after firmware updates, and try it with your router off.
• For a heat load, prefer a controller with nothing to negotiate. A rocker switch shows by sight that the contact is closed. Intermatic’s electronic 24-hour time switches with battery carryover keep their schedule through an interruption and have a MANUAL override.
• A smart plug is a switch, not a temperature control. Merck puts a thermostat between heater and animal.

For the tank, the time-critical steps are the 24-hour feeding hold above and, for a reef, the fresh-water top-off.

Generator Safety: The Mistake That Kills People

If you run a generator for a heater or reptile lamp, the carbon monoxide risk is to your whole household. The Consumer Product Safety Commission says never run a portable generator indoors, in a garage, basement, crawlspace, or shed. Run it outside, at least 20 feet from the house, exhaust pointed away from windows, doors and vents, and look for a model with a built-in CO shut-off.

CPSC estimates an average of nearly 100 people die in the U.S. each year from portable-generator carbon monoxide poisoning. That is a 2019 to 2021 annual average (Directorate for Epidemiology, February 2025), a preliminary estimate that is typically revised upward for recent years, and it covers consumer portable generators only.

Building an Aquarium and Reptile Outage Kit

• A battery backup air pump sized to your tank, with fresh cells staged or a rechargeable kept charged. Check that a reef backup actually drives your pump.
• Heat packs plus a towel or sock barrier; check the temperature rather than trusting a pack count, and write each pack’s rated hours and best-before date on its box.
• A battery or manual thermometer that reads in the dark and resolves to a tenth of a degree, for the cooling-rate timer.
• A net and a heavy-duty bag, kept together; a reptile soaking bowl (ASPCA); backup water (fill the tub ahead of a forecast outage); a hygrometer if humidity matters to your species.
• On paper: your species’ temperature range and your vet’s and exotics vet’s numbers.
• A tested power-restore setting on every plug, plus a hand-operated switch for any heat load.
• For a reef tank, your circulation pump’s draw in watts or amps (CoralVue’s formula needs it), taped inside the cabinet door.

Want the go-bag list on paper? Get the free printable go-bag checklist.

See pets and power outages, generator carbon monoxide risks for pets, portable power stations for pets and pet medication and refrigeration during an outage. Feeders and fountains also stop with the pump; see how long an auto feeder lasts in a power outage.

About These Products

This page compares published specifications; we did not test the products. We don’t sell aquarium or reptile equipment or take sponsorships, and we’re reader-supported through the disclosed Amazon links above; commissions never touch which products we recommend. Full methodology at /review-methodology.

SnuggleSafe, UniHeat, Aquarium Co-Op, Penn-Plax, Aquatop, EcoTech Marine, CoralVue, Pangea Reptile and HotHands are trademarks of their respective owners; EmergencyPetPrep is not affiliated with or endorsed by any of them.