How Long Can Fish Survive Without Power?

Colors to doomed spaces and brightness to the mind are what fish tanks bring into the lives of owners.

Fishkeeping is easy, but the most dreaded situation for an aquarist is a power outage, be it for hours or days. Are you stressed about how long your fish will sustain when there is a power cut?

Your fish and other aquatic animals can survive 2-6 hours without electricity, depending on the fish species, tank size vs. the fish population, and temperature. The safety of your fish also depends on how prepared you are to tackle such occurrences. 

Check out the article to be aware of what to do in this scary situation if at all it hits you.

How Will A Power Outage Affect Your Aquarium?

The whole aquarium functions on electricity, and during a power cut, the lives of the fish are at stake. A power cut for a few hours may not affect the aquarium environment much, but extended hours without power can cause the death of the fish.

This is what happens when there is no power.

Oxygen Levels Go Down

When the electricity goes out, the air pump will stop functioning, causing depletion of oxygen level. The power heads, if connected, aid in the agitation of the water, resulting in oxygenated water.

The more the oxygen level drops, the higher the chances of the aquarium fish passing away.

Betta fish or gourami can still manage by swimming up to the water’s surface and gulping air, but it’s not the case with most fish.

Spike In Ammonia

During extended blackouts, with every gadget becoming unresponsive, the filtration system stops working too. The leftover food and bio-waste of the fish in the aquarium water lead to an increased concentration of ammonia.

Fish swimming in the poopy water will be exposed to the toxic ammonia, endangering their lives.

Unregularized Water Condition

Originating from different climatic conditions, fish need similar water temperature to be healthy. For example, the tropical fish tank requires warm water to thrive, whereas some species, like goldfish and pearl danio, dwell in cold water temperatures.

When there is a power outage, the aquarium heater will stop operating, making it rather difficult to keep the water temperature suitable.

The water will either become too hot or too cold, so acclimatizing to the surrounding might become inappropriate for your fish.

How To Safeguard Your Livestock in Fish Tanks During Power Cut?

Oxygen Levels

When the oxygen level drops during blackouts, you can use the following hacks to improve the situation.

Manual water changing

  • You can change large batches of water to dissolve more oxygen from the freshwater in the aquarium.
manual water changing

Battery backup

  • Connect the essential aquarium setup to inverters or generators to power the tank. You can also use battery-run devices such as battery-powered air pumps or filters for movements in water to generate oxygen.

Agitation of water

  • Stir the water in the aquarium or hang a dripping container to agitate the water. The air bubbles will exchange the atmospheric oxygen in the water, leaving the tank oxygenated.
agitation of water

Cooling the water

  • Increased temperature of water in the tanks also depletes the oxygen concentration. You can cool it down by changing the aquarium water with some cold water to increase O2 levels.

Filtration System

When the filtration system stops working during a power outage, the ammonia levels increase due to the waste overload.To balance the toxicity in water and remove the ammonia concentration, you can use zeolite in recommended quantities.

A water change in the aquarium will help replace contaminated water with fresh water.

Clean the filter with all the unwanted particles collected over time so that everything is fresh to use when the power comes back.


The good bacteria in the wet filter media help break ammonia into less harmful nitrate compounds. The nitrate concentration is then filtered out, which can be powered through batteries when there is no electricity at your place.

Tank Temperature

Maintaining water temperature is crucial for fish accustomed to their natural water condition.

You can use heat packs alongside the aquarium wall or mix hot water into the tank to create warm and tropical water conditions for the fish to survive.

Similarly, fusing some ice cubes in a plastic bag into the water will decrease the temperature, which is suitable for cold water dwellers such as rainbow shiners or white cloud mountain minnows.

Please check the initial temperature so that you can regulate it sparingly.

How To Prepare For A Power Outage?

Do you experience regular power outages in your area? Or do you live in a natural calamity-prone region where electricity is uncertain at times?

In any of these cases, it is best to be prepared to avoid regretful situations later.

Get geared

Invest in some gadgets, equipment, and materials to save your aquatic world from diminishing during power outages.

Battery-powered air pumps

Battery-powered air pumps are a boon during darkness or power outages.

battery powered air pumps

A battery-powered air pump operates on D batteries and lasts up to 10 hours on average. It aerates the tank through air stones, where air bubbles release oxygen into the water.

It is convenient equipment that will not punch a hole in your pocket.


Inverters are a feasible option as they are portable and run on battery. The inverter converts DC from the battery into AC power, which supports the tank machines that are vital for the fish’s health.


Generators will be the best rescue when you suspect a prolonged power outage, as it functions on gas. You can readily get gas from a station or siphon it from your automobile.

It is a hefty investment but will save you if you have a large aquarium setup to power various gadgets that will keep your fish alive. Whether it is the air pumps, the filtration system, the water heater, or the lights, everything will operate without interruption till the gas lasts.


An uninterruptible power supply (UPS) will allow you to buy time before preparing for a power outage. In addition, the equipment connected to the aquarium does not abruptly shut down when the power goes out; instead it keeps them running for a while.

It is ideal when a power outage is rare and lasts less.


The aquariums made of the glass work as an efficient insulator as it is great at retaining heat.

Besides, wrapping the aquarium in warm blankets will help protect the heat loss during power disruption in chilly weather.

Check the population of the fish tank

How long the fish will live without power depends on how many fish are in one tank. The higher the tank’s population, the higher the chances of the fish losing their lives.

More fish directly means higher oxygen consumption, a scarce resource during a power outage. The waste generation will also increase, causing a rise in ammonia levels, toxifying the water.

If your tank is overstocked, be prepared to transfer a few fish to another tank temporarily.

Keep track of fish food and fish waste

Fish can go without food for days, so you can skip feeding your fish on days without electricity. When the fish consumes food, it also consumes more oxygen for metabolic activities.

It is better to refrain from feeding fish during long hours of power cuts so that there is optimal utilization of the existing oxygen concentration. Also, there will be less ammonia aggregation owing to reduced fish waste.

Tips To Keep Your Fish Calm And Healthy During Power Outages

  • Monitor your fish tank regularly during power outages to observe their behavior. Any unusual activity like rapid gill movements will indicate that the fish needs care.
  • Dim the brightness of the space around the aquarium. Fish are diurnal creatures that become sluggish in the dark. The inactive fish in a dark environment will, therefore, consume less oxygen.
  • You can lower the level of water in the aquarium. If the water level is kept a bit low, it will make it easier for the fish to swim at the surface for oxygen exchange in the air.
  • It would be best if you prioritized which equipment to be backed up by the battery. When there is no electricity, and you have limited access to power through batteries, connect the aquarium equipment most crucial at the moment. It could be your heater or air pump.
  • A wide aquarium will help in such situations. The large surface area will be in contact with air, resulting in a higher concentration of O2 in the aquarium.
  • You should choose the fish tank community wisely. Some species are bottom dwellers like bass or eels, while some, like tetras, swim in between, and bettas usually inhabit the top. A combination of different water level species will help in the consumption of oxygen content at all levels.
  • Be equipped to store water during storms or floods. The tap water will be contaminated during downpours; hence caching clean water for the aquarium is necessary.


Will my fish die during a power outage?

Whether or not your fish will sustain a power outage depends on various factors, such as weather, availability of alternate resources to aquarium equipment, and the number of fish in the tank.
But hold back before stressing, as the fish can survive this dreaded situation if you equip the aquarium with substitutes. For example, battery-powered air pumps, insulators, or chemicals to clean water can be used to revive the deteriorating environment in the tank.

Which fish can survive without a filter?

Fish that can hang out in smaller tanks or bowls do not require an automated filtration system. Some fish species that do well in such conditions are:
Zebra danios
Dwarf puffer fish
Betta fish

Will tropical fish die without a heater?

Tropical fish are accustomed to warm climates; hence they will die if they stay where the ambient room temperature is low due to cold weather. A heater will help in keeping the tank warm.

What chemical can be used to oxygenate the aquarium?

Hydrogen peroxide in restricted quantities will add oxygen to the tank water. Mixing hydrogen peroxide in water will generate enough oxygen for the fish to survive emergencies.
Please note– Some fish, like blue gourami and suckermouth catfish, might be intolerant to chemically dissolved oxygen—research well before using this chemical treatment in your aquarium water.

How long can marine reef tanks survive without power?

Considering that the reef tank is not overstocked, marine fish species can sustain with no filtration, heater, or air pumps for a few days (2-3 days). An alternate oxygenation source is a basic necessity during a power outage for marine aquariums.

What are the alternatives for air pumps in aquariums during a power outage?

When the air pumps stop working due to a blackout, it won’t be easy to maintain the oxygen levels in the fish tank. But before you panic, be equipped with these alternatives to aid in such unforeseen situations.
You use a cup and pour out some water from the fish tank and pour it back in slowly, creating surface agitation in the water. The air bubbles created will oxygenate the water.
Put some aquatic plants in the fish tank to maintain the oxygen and carbon dioxide balance.
Use a battery-powered air pump or powerhead to create a movement that will keep the water oxygenated.


With great pleasure comes great responsibility when it comes to keeping a pet. This guide will prepare you as a fish keeper to tackle situations like power outages.

Being cautious and well-equipped beforehand will save your fish from dying during no-electricity times.

For any other query, please drop a comment, and I will get back to you with an answer.

Leave a Comment