How to Keep a Fish Tank Warm Without a Heater

Many of us are fond of keeping fish and must know how to keep a fish tank warm without a heater. Tropical fish and bettas are some of my favorite ones. After adopting this hobby you have to be very careful about all the advanced techniques and accessories for your fish and fish tank. The most important thing for your aquarium water is how to keep betta fish warm.

how to heat up a fish tank without a heater

In that case, many types of heaters are available in the market to fulfill this need but nowadays electricity fall has become a major problem in keeping them warm without a heater. Energy backup has become a vital need that must be provided as soon as possible to maintain the temperature. It is our responsibility to know how to keep fish alive when the power goes out.

How to Warm up Your Fish Tank Without A Heater

If your fish tank does not have a heater, here are some ways to warm it up:

  1. Insulation: You should wrap the tank in insulating materials such as Styrofoam or insulating foam. This helps retain heat and prevents temperature fluctuations.
  2. Warm room temperature: It is best to keep the aquarium in a room with a stable, warm temperature to help warm up the water naturally. Do not place it near drafts or areas that are cold.
  3. Heat packs: After activating the hand warmers or heat packs, secure them to the tank exterior or place them outside the tank as supplemental heating.
  4. Heat lamps: A heat lamp placed above the tank will provide warmth. The lamp should be properly installed and not overheat the tank.
  5. Floating containers: In the tank, place a container filled with warm water to gradually raise the temperature. Keep a close eye on the water temperature to prevent sudden changes.

These methods are temporary and may not be suitable for long-term use or in the winter season. The best way to maintain a stable and appropriate temperature for your fish is to invest in a reliable heater.

Ways to Heat Up a Fish Tank Without Using a Heater

I’ll explain some useful elements to gradually heat up the tank’s water without the heater.

It may take some creative thinking to use some of these add-ons, but you need to give them a shot if you’re considering a heater-free setup

Here are some Alternative Tricks and Solutions that explain how to heat aquariums water quickly without a heater:

1. Use a Blanket or Heavy Towel in Emergency

This can be proven the fastest and most readily available solution in every home. All fish keepers must have a blanket and heavy towels at home. Your main goal is to keep fish away from cold air getting into the tank.

A heavy blanket is enough for large tanks. This will create insulation around the tank. Compared to a thin towel, a thick towel will work effectively.

While using a towel or blanket, the water temperature will remain within an aquarium for as long as it is big enough to avoid freezing.

2. To Keep Fishbowel Warm – Use a Heating Mat

Usually, heating mats are good for small tanks like fishbowls. But at the same time, they can increase the water temperature in the small aquarium.

By using heating mats, a buffer layer must be added to them. This method will protect your fishbowl from hot spots and glass cracking.

Considering glass as the best heat conductor isn’t enough, so this is not the best add-on. The method works best for keeping a fishbowl warm.

3. Choose A Lid/Hood/Canopy To Cover The Tank

To keep a fish tank warm without a heater, cover it by using a lid or hood, or canopy. It is the common and easiest way to make limited contact with water and cold air passing into the tank.

The aquarium’s lid will protect it from the elements and help you build up warmth quickly. The tops of most tanks can be easily removed to allow for access to the aquarium insides to manage all interiors.

Covering the tank with a lid can reduce the oxygen supply which will not be good for fish lives, but at the same time by using an air pump and an air stone oxygen level can be maintained.

4. Use Warm Water For Water Changes

Maintaining a tank’s water temperature without a heater is not a challenging task in which you have to make frequent stops to make it warm as soon as possible.

This method needs full attention and monitoring. It’s not a long-term solution but it will help you maintain the temperature for a while.

First of all, you need a container that can hold boiled water easily or is unbreakable.

Fill half of the container with boiled water. Ensure the water container doesn’t tip over when you place it on top of your aquarium. Don’t let it touch the aquarium’s sides or your little friend could get squished.

Mix a portion of boiling water with room-temperature water, but do not add boiling water directly to the tank (even if there aren’t any fish yet).

You will need to store extra water for the water changes if you choose to use this method to warm up your tank.

It will be necessary to raise the temperature slowly, of course. Some fish species can be harmed if raised more quickly than 1° per hour.

5. Place the Aquarium in a Heated Room/ Close to a Heater/ in Sunlight

In cold climates, this type of situation causes anxiety among aquarists. Without a heater, the owner of an aquarium has to do lots of work to keep the aquarium water warm.

One of the popular solutions is a heated room available in almost every room of the house. A consistent heater is placed in colds to warm up the room. The placement of an aquarium in a heated room will stabilize the water temperature. No heat means that the temperature fluctuates and can cause serious stress out bettas. This affects their immune system, leading to weaknesses and illness. Fluctuations should be between 1-2 Fahrenheit.

To heat an aquarium, you can place it in sunnyside, but be careful about direct sunlight, because it can cause algae growth on the fish. A 6-hour day is enough for them to receive natural sunlight. It is a great way to warm up the aquarium water and takes very little time.

6. Inefficient, Low-Quality Filters

All of us know that heat is generated by electric systems and an inefficient mechanical system will generate more heat that can be suitable for your aquarium in the absence of a heater or heating system. A low-quality filter will also work in that condition. When water flows into the filter, it will constantly be heated.

In contrast to strong lights, sun, or heated rooms, using the filter is a constant and better way to heat your tank.

Using this method, you have to test different filters that can provide the heating system you need for the tank.

It would help if you also were very careful about creating consistent temperatures through the filter. Filters that are not energy efficient can work improperly throughout the day. Temperature changes can result from using these types of filters. A box and receipt must be saved in this case, so that you can change or return the filter.

7. Insulate Your Tank, Glass Walls

If you want to insulate the glass walls of your aquarium, you can choose from the following options: 

In addition to the insulating method, other methods can be insufficient to keep your aquarium warm without a heater. How long you would like to heat your aquarium by insulating it, you must know the temporary and permanent methods.

1. Wrapping a blanket is a temporary method just for a few hours. Cover the aquarium with a blanket without dipping into the water. it is a good option for temporary insulation around the sides and top of the aquarium.

2. Another option is to place a Styrofoam container to cover the glass walls around the whole aquarium. Styrofoam is a lightweight material that is easy to wrap around aquariums. Place a heat pack inside first. Heat packs for shipping work, but you can also use reusable ones since you’ll be able to recharge them while you’re there.

 Insulating the sides and back of the aquarium is the best permanent solution.

Without Power, can you Heat a Fish Tank?

Most of us would like to know how to heat a tank without power to warm up aquariums. As we all know, heaters are used mostly to heat fish tanks with power and it is not possible to run them without power.

Heat pads and hot water bags can be used for heating the fish tank without electricity. Candles can also be used to heat the tank however, this method is only suitable for tetra fish. You must be very attentive when doing this.

The burning of candles will produce a soothing effect on the water. This is a temporary procedure that must not be done long-term.

how to keep betta fish warm without a heater

Why do Tetra Fish Need an Aquarium Heater?

To keep the fish healthy and safe, choose an aquarium heater that will provide them with proper heat and maintain the required temperature.

A heater must be used for tetra fish to live in constant temperatures for a long time. Betta is undoubtedly affected by changing water temperature even though their sensitivity to environmental parameters is rather low.

It can negatively impact the fish’s health. For this reason, you must keep the tank’s water temperature properly. A high-quality aquarium heater prevents the fish from harm. Don’t be reckless in the issues of the health of the fish.

Temperature Changes and Fish: Which are the Most Affected?

Fish that are most affected by water temperature changes are tropical fish. They are not suitable for tanks without a heater as they are sensitive to temperature fluctuations, which can lead to stress and make them more susceptible to diseases. The following fish thrive in consistent tropical environments with temperatures between 75-80 degrees Fahrenheit:

  • Neon tetras
  • Guppies
  • Bushy nose plecos
  • Congo tetras
  • Cherry barbs
  • Swordtails
  • Dwarf gouramis
  • Panda cory catfish
  • Betta fish

In addition, coral reefs require stable water conditions and UV light to thrive. Maintaining a steady water temperature between 75-78°F is challenging in a minimalist system without a heater.

How Sensitive Are Fish to Temperature Changes?

Fish are highly sensitive to temperature changes, particularly aquarium fish, as they are typically tropical species adapted to warm, stable water temperatures. Even a slight fluctuation can cause stress and weaken their immune system, making them susceptible to diseases.

Cold-water fish, such as goldfish, are more resilient and can tolerate a range of temperatures, but prolonged exposure to extreme temperatures can still be harmful to them.

It is important to maintain a suitable and consistent temperature in the aquarium to ensure the well-being of the fish.

Frequently Asked Questions

1. Do aquarium lights work as a heater for aquariums?

The answer is a definite NO as aquarium lights can produce heat but in extremely small amounts. If you decide to depend solely on the light heat, that is going to be very dangerous for the fish.

The result is that it is not a good idea to turn on the lights without a heater. if lights must be used, turn on strong lights, but not the heater substitute.

2. Is the size of my aquarium heater important?

The size of your aquarium heater does matter. It is important to choose an appropriately sized heater for your tank. Calculate the wattage needed per gallon and select a heater accordingly.

For example, if you have a 20-gallon tank and need to raise the temperature by 18 degrees Fahrenheit, a 75-watt heater would be suitable for maintaining the desired temperature.


Nevertheless, there are many ways to keep your beta tank warm without heating it, but as mentioned above, this isn’t a permanent solution. There are no other ways other than arranging the best quality heater for your aquarium in order to maintain fish health and ensure they can live a long time.

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