How to Heat a Fish Tank Without Using Electricity

Cichlid tank decorated with live and fake plants

People used to maintain fish in aquariums before the introduction of electricity. With a few "modern innovations" to keep the fish warm, even tropical fish may be preserved. External heat sources, such as tiny gas burners, were used under the aquarium in the past to keep the fish warm. Unlike the glass or acrylic tanks we are acquainted with today, aquariums were carefully constructed with a bottom that would retain heat. If you lose electricity, be prepared to take the following procedures to ensure the life of your fish.

Check to see if your fail-safe devices have activated as soon as the power goes off. Backflowing airline tubing and sump shutoffs are used to prevent water from draining out of the aquarium. It's vital to keep the heat in the water if you have a heated tank. Wrap your tank and any filtration with blankets, towels, or cardboard to keep them warm over the winter. Don't forget to cover the top of your tank, but make sure the oxygen supply isn't cut off.

Resist the impulse to check on your fish every few minutes. You will lose heat every time you remove the blankets. Place your thermometer in your tank where you can see your fish and their present surroundings without having to unwrap them. Rather of using an electronic thermometer, you'll need to use a to keep track of your temperature. Digital thermometers that are powered by batteries, on the other hand, will continue to function.

If you can't insulate your tank, you'll have to rely on hot water bottles to keep the temperature up. Remember that this approach is more difficult and might result in larger temperature changes. Use fish-safe containers and regularly condition your water in case some seeps out. Containers that have previously held home cleaning chemicals should not be reused. If you have a gas water heater in your house, you should be able to keep the aquarium water warm by changing out the water bottles as needed. In the event of a power outage, an electric water heater will no longer function, although the water in the heater tank may remain warm for several hours.

If you have a gas stove, you may warm the aquarium by boiling water in a skillet and pouring it into the bottles. Do not fill your hot water bottles with boiling water. If you want to keep your aquarium water at approximately 80 degrees Fahrenheit (27 degrees Celsius), use water that is between 100 and 120 degrees Fahrenheit (38 to 49 degrees Celsius). Your water bottles will need to be replaced regularly, but the temperature of your tank will not fluctuate as much. Wide temperature changes can be harmful to fish, as opposed to a steady, progressive cooling.


Invest in a couple bait bucket aerators to ensure that your fish have enough oxygen. These are battery-powered rather than plug-in, and are an excellent investment for any fish owner. Make sure the battery packs are stored above the aquarium's water line, as with other aeration equipment. If the batteries fail, the water in your tank will not be siphoned out accidently.

Place one aerator in the center of your aquarium or two at opposing ends. Aerators bring the temperature of your water closer to that of the ambient air, thus positioning them higher in the house will keep the air they contribute warmer. If at all feasible, insulate the airline tube.


Do not´╗┐ cover the battery units. This can cause them to overheat and stop working.

Water Quality

During power outages, keep an eye on the tank temperature and water quality. Expect none of your biological filtering systems to function correctly. Regularly test your water quality and make sure you're prepared to undertake further water changes if necessary. This may need storing additional water in order to keep the water warm enough to do water changes.

If you're going to make a water change on a heated tank, you'll need to get your water to the same temperature as the aquarium water. To bring your fresh water to the right temperature, heat a little bit of it and gently add it to room temperature water. Never immediately pour hot water into your aquarium!


Limit your fish's feed if you want to reduce their ammonia output when the biological filter isn't working. Thankfully, your fish's metabolism slows and they get less hungry when the temperature drops. Depending on how long you intend to be without power, you may need to feed your fish and other aquatic creatures a little quantity of food once a day to ensure their survival.

If you give your fish a frozen diet, it won't last long if you don't have access to power. If the freezer power is down, you may fill it with ice in an ice chest to keep it for longer. If your frozen diet defrosts, you must feed it immediately or discard it. If you try to re-freeze the product, you risk damaging it and making the meal unhealthy. If you generally eat just frozen food, you may need to purchase flake or pelleted food to supplement your diet when the power is out and frozen food is unavailable.

Critical Steps to Keeping Your Aquarium Toasty

  1. Check fail-safe systems as soon as possible.
  2. Insulate your tank, top and filtration included.
  3. Add battery operated bait bucket aerators.
  4. at least three to four times daily.
  5. Add warm water bottles as needed to keep the water temperature at the appropriate level.
  6. Test daily. This includes your , pH, and kH at a bare minimum.
  7. Resist constantly checking on your fish. Every time you take a peek, you are letting heat out.

Susceptible Species

Many fish species are sensitive to temperature differences. Certain marine tropical fish are finicky about their water temperatures and are especially vulnerable to difficulties if the temperature isn't kept steady.

Species that have low tolerances for poor water quality will be particularly vulnerable. Because your biological filtration system will be unable to work, your tank's ammonia level will rise. Marine fish and coral species, like temperature, are the least tolerant to increased ammonia levels and will need to be accommodated if they are to live.

In order to photosynthesize, corals will also require UV radiation. You should anticipate your corals to suffer a little if you are unable to utilize your tank lights for a few days. Some coral caretakers use mirrors to reflect sunlight into their tanks, allowing them to get more light. Be aware that this strategy will also accelerate your algae growth!

Best Species to Survive

Species that can handle a wide range of water temperatures, don't require a heater, and aren't excessively sensitive to times of somewhat poor water quality will be able to withstand a long-term power outage. Some tropical fish will perish if the water temperature falls below 65 degrees Fahrenheit, but many carps, such as goldfish and koi, and minnows, such as the White Cloud Mountain minnow, are cold-tolerant.

Many carp species, such as goldfish, can withstand harsh conditions. They can withstand a broad variety of temperatures as well as decreases in water quality. Comet goldfish are often more durable than flashy types.

These little striped fish can withstand temperatures ranging from 64 to 75 degrees Fahrenheit (18 to 24 degrees Celsius), as well as relatively consistent interior room settings. They come in a variety of short and long fins, as well as vibrant hues.

Advanced Planning

To prepare for a power outage, what should you have in your toolkit? You may get a head start on keeping your aquarium temperature stable if you know a power outage is on the way. Here's a list of things you'll need:

  • Insulation materials (blankets, towels, etc.)
  • Bait bucket aerators
  • Standard glass aquarium thermometer
  • Extra water for water changes and water conditioner
  • Ability to heat water (stove, fireplace, etc.)
  • Clean plastic water bottles to fill with warm water and put into the aquarium

Keeping Systems Cool

If the power goes out, those of you using to keep your aquarium temps down will be in the same boat as others who don't have enough heat. Overheating aquariums may also occur amid power outages throughout the summer in hot places that rely on air conditioning. Here are some suggestions for the polar opposite of the temperature scale:

  • Allow air to circulate around your tank and all your equipment. Use fans if necessary.
  • Minimize or eliminate exposure to direct sunlight.
  • Take the lid off your aquarium and replace with netting.
  • Add additional aeration as explained above. Do not insulate the airline and keep the units above the water line, but in a cool location.
  • Use ice in bags or bottles placed in the aquarium to keep the water cool.


"Dealing With Aquariums And Ponds During Power Outages. North Carolina State Veterinary Medicine." ;