How to Heat a Fish Tank Without Using Electricity

Cichlid tank decorated with live and fake plants

People kept fish in aquariums before the discovery 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 created with a bottom that would retain heat. If you lose electricity, take these actions to safeguard the life of your fish.

Make sure your fail-safe devices are engaged 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. Remember to cover the top of your tank, but be careful not to shut off the oxygen flow.

Resist the impulse to check on your fish constantly. 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. To keep track of your temperature, you'll need a rather than an electronic one! Digital thermometers that use batteries will still work.

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. Reusing containers that formerly held home cleaning solutions is not recommended. If you have a gas water heater in your house, you should be able to keep the aquarium water warm by changing 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). Water bottles will need to be replaced often, but the temperature of your tank will not change as much. Wide temperature changes might be more harmful to fish than gradual cooling.


Invest in a couple bait bucket aerators to ensure that your fish have enough oxygen. These work on batteries instead of electricity 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 for 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 get the desired temperature, heat a tiny bit of your fresh water and gently add it to room temperature water. Never fill your aquarium with boiling water!


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 tiny quantity of food once a day to keep them alive.

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 when 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 resistant to increased ammonia levels and will need to be adapted to live.

To photosynthesize, corals will also require UV radiation. You should expect your corals to suffer significantly if you are unable to utilize your tank lights for a few days. Some coral caretakers use mirrors to reflect sunlight into their tanks, giving them 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.

Goldfish and other carp species are tenacious survivors. 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 short and long fins, as well as bright hues.

Advanced Planning

To prepare for a power outage, what should you have in your toolkit? If you anticipate a power outage, you may get a head start on keeping your aquarium temperature stable. What you'll need is the following:

  • 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 other end 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." ;