How To Keep Betta Fish Warm Without a Heater

Bettas are gorgeous tropical fish that come in many species and varieties.

This popular aquarium fish originates in various parts of Southeast Asia. This means it needs specific water parameters to thrive.

They do best when the water temperature is between 78-80° degrees Fahrenheit (25.5-27° C).

Most fish owners install a tank heater to keep the tank water within this range. But if your fish tank heater stops working — or if you have yet to buy one — there are other ways to keep the fish tank warm. 

Note: The ideas listed below are only meant to be short-term solutions. An aquarium heater is the best way to keep a warm, stable water temperature.

how to keep betta fish warm without a heater atf

#1 Insulate the Tank

Keep the aquarium water warm by insulating the tank. This method is a great temporary solution for when your tank heater isn’t working.

To insulate the tank, wrap it with blankets, towels, or other insulating materials. These materials keep heat inside the tank so the temperature doesn’t drop too quickly.

When using this method, be careful not to cover the entire top of the tank. Betta fish have a labyrinth organ, which means they must go up to the water surface for gas exchange. Covering the top of the tank will prevent them from doing this. 

Here are some materials to consider using for insulation: 

  • Blankets or towels: These are easy-to-find objects, making them perfect for emergency use. They’ll do a good job of keeping the heat inside the tank and preventing its escape. But they’re not the most effective option. 
  • Styrofoam: Buy Styrofoam sheets or panels, and use them to insulate the fish tank. Styrofoam has strong insulation properties and is cost-efficient. 
  • Reflective insulation: This type of insulation reflects heat away from the tank. Reflective insulation won’t make the water warmer, but it will keep the water from cooling.

Layered Insulation

Instead of choosing one material, use a few different insulation materials. Doing so may increase heat retention and do a better job of keeping the tank insulated. 

For example, you might use one layer of blankets followed by another layer of styrofoam. 

#2 Move the Tank

Another option is to move the tank from its current location to a warmer one. 

The key is to move it to a warmer location with consistent temperatures. Avoid places near windows or air vents, as they’re prone to temperature fluctuations.

If your home has a second floor, it may be a good relocation spot. Heat rises, which means the tank water will likely remain warmer upstairs. 

In some cases, aquariums enjoy placement in partial or direct sunlight. The sun will both provide adequate lighting for your fish and plants and heat the tank well.

Experts suggest giving your betta about six or seven hours of sunlight per day.  

After moving the aquarium, regularly check the water temperature for any fluctuations. Betta fish can experience temperature shock if the temps change too quickly. 

#3 Use a Heating Pad

heating pad for betta fish

A heating pad is useful for keeping aquarium water at the proper temperature. The warmth from the heating pad will increase the water temperature and help keep it stable. 

To use the heating pad, ensure you place a buffer layer of material between the pad and the tank surface. Glass tanks are prone to poor heat conduction.

Direct heat application may cause the glass to crack.

Also, heating pads work best for smaller fish tanks or bowls. If you have a large tank, this option may not be effective. 

#4 Use Warm Water Bottles

Another method to get water to the proper temperature without a heater is to use warm water bottles. 

Fill plastic water bottles with warm water and place them around or inside the tank. Make sure to seal the water bottles properly, and watch the water temperature.

With this method, the warm water bottles gradually increase the fish tank temperature. This is important, as betta fish may become stressed or ill with sudden temp changes.

Gradual heating is a safe and effective way to raise the temperature. 

#5 Stronger Lighting

Aquarium lights are good for short-term water heating. 

But while this is an effective method, aquarium lights may cause overheating. To avoid complications, check the water temperature often.

If you notice the water getting too warm, turn off the aquarium lights or move the fish tank. Some lighting solutions allow you to choose specific hours for lighting.

This may help avoid overheating, and it’s also useful for planted tanks. 

Ensure you don’t put the lights too close to the fish tank. This will cause overheating and may even damage the glass. 

#6 Increase Room Temperature

Increasing the room temperature is a simple and effective way to keep your fish tank warm. As the room temperature gradually increases, so will the water temperature. 

Note: this method might not apply in the event of a power outage. Also, it’s more costly and less energy-efficient than many other ideas on this list. 

Increasing the room temperature will work for shorter periods of time, though.

#7 Socks or Gloves With Hand Warmers

Another way to keep your fish tank warm is with hand warmers. 

Activate the hand warmers and place them inside socks or gloves. Then, put the socks or gloves around the fish tank. 

The heat given off by the hand warmers will increase the water temperature. Over time, you may need to switch out the hand warmers for new ones. 

This is not the most effective option, but it will work for short-term use. Ensure it’s working (and the water’s not overheating) by regularly checking the temperature.

#8 Temporary Tank Cover

tank lids help keep betta warm

If you don’t already have a lid for your betta fish tank, consider buying or creating one. 

One benefit of having a lid is the improved heat retention. The lid curbs the amount of heat the tank loses, helping keep the temperature stable. Having a lid also prevents excessive evaporation. 

There are several materials to use to make a temporary tank cover. Some materials to consider include the following: 

  • Plastic wrap
  • Cardboard
  • Plexiglass
  • Mesh

Creating a lid will involve cutting the materials to size and securing them in place.

When doing this, ensure you leave enough room at the top of the tank for your betta to perform gas exchange. 

#9 Rice Sock

To use this method, fill a sock with uncooked rice and microwave it for 1 to 3 minutes.

Take it out of the microwave, ensuring it isn’t too hot and has reached the desired temperature. 

Place the rice sock near the tank to increase the fish tank temperature. 

With this method, you’ll want to continuously check the water temperature. The goal is to keep the temperature stable and within optimal parameters. 

After a little while, reheat the rice sock (it will lose heat over time). 

#10 Submersible LED Lights

Buy submersible LED lights to help keep your aquarium warm in a pinch. 

These lights produce enough heat to raise the tank’s temperature a bit. Another benefit is in how lighting helps your aquarium plants grow better.

This method is best used in conjunction with the others on this list. By themselves, LED lights don’t produce enough heat to keep temperatures warm long-term.

#11 Water Change With Warm Water

warm water to help bettas

Raise your betta fish tank temperature by performing a water change with warm water.

Frequent water changes are already an essential part of aquarium upkeep.

If you’re worried about a drop in tank temperature, consider switching out 20% to 25% of the water with warm water. 

This method will increase the water temperature more gradually. Betta fish do best with gradual water changes. Sudden temperature changes can make them ill or stressed.

#12 A Smaller Tank

Another way to better maintain the fish tank temperature is to move your betta to a smaller tank or fish bowl.

Buying a nano aquarium means you’ll spend less time correcting the water temperature. The smaller the betta fish tank, the faster it will warm up. 

This method is not meant to be a long-term solution, though. 

Bettas have plenty of space in their natural environment, so they prefer larger tanks. Having a larger tank also helps keep ammonia levels lower, whereas a nano tank lets ammonia build up. 

We recommend an aquarium size of at least five gallons for a single betta fish.

A 10-gallon tank is even better, though. Increase the tank size as you get more fish or decorations to avoid overcrowding.

#13 Non-Energy-Efficient Filter 

Using a non-energy-efficient filter is a great way to get your fish tank warmer. 

This type of filter produces more heat than energy-efficient filters do. The heat it gives off helps raise the fish tank temperature. 

Of course, this method will mean you pay more for energy. This solution is only for short-term use, and we recommend trying the other ideas on this list first.

Frequently Asked Questions

Can aquarium fish survive without a heater?

This depends on the fish species. Most species of betta fish can survive without a heater, but we still recommend getting one. 

Bettas are tropical fish, meaning they thrive in warm water temperatures.

Some fish owners are able to keep the tank warm enough without a heater.

But having a heater makes the process easier and more cost-efficient. 

If you prefer not to buy an aquarium heater, consider getting coldwater fish.

These are fish species capable of surviving in cooler water temperatures. 

How do I temporarily heat my fish tank?

There are many methods for heating your fish tank.

Some of the best options from our list include the following: 

– Insulating the betta fish tank
– Moving the tank to a warmer location
– Heating the water gradually with warm water bottles
– Using an aquarium lid to keep heat inside more effectively

These are only temporary solutions, though. We recommend getting an aquarium heater as soon as you’re able to. 

How cold is too cold for tropical fish?

Most tropical fish thrive in temperatures between 75-80° degrees Fahrenheit (24-27° C).

Betta splendens do best between 78-80° degrees Fahrenheit (25.5-27° C).

But there is some room for fluctuation. Bettas are hardy fish capable of surviving a range of water temperatures, but only for so long. 

For the best results, keep the water temperature no lower than 75° degrees Fahrenheit (24° C).

How can I heat my fish tank water faster?

If the alternative methods in this article aren’t working, consider buying a heater.

Fish tank heaters are useful for keeping the water temperatures warm and stable. Since they run automatically, you don’t have to worry about always checking the temps.

Ensure you buy the correct size when shopping for a fish tank heater. The size range, in gallons, should be visible on the heater’s packaging. 

Learn More About the Proper Care of Bettas

There are many ways to keep your fish tank warm without a heater.

But we recommend buying an aquarium heater anyway. The methods in this article are only temporary solutions.

Follow us for more information on betta fish care, and share this post if you found it helpful! Bettas are among the most beautiful tropical fish out there.

Our goal is to help betta lovers care for them well.

How useful was this post?

Click on a star to rate it!

As you found this post useful...

Follow us on social media!

We are sorry that this post was not useful for you!

Let us improve this post!

Tell us how we can improve this post?



Wesley Oaks has a background in web publishing and decided to combine his skillset with his enjoyment of betta fish. When he isn’t working behind the scenes for Betta Fish Bay, he’s homeschooling his kids and soaking up quality family time.

Follow Us on Facebook!

Get betta fish fun facts right on your Facebook feed and see when we share new content by following our page on Facebook.

blue betta fish

Advertiser Disclosure

We are reader-supported and may earn an affiliate commission when you buy through links on our website. To be 100% clear, you should assume that we will earn a commission on any product you purchase after clicking on links or images on this website.

Our affiliate partners include but are not limited to

In addition, we generate revenue through advertisements within the body of the articles you read on our site.

Although we only recommend products that we feel are of the best quality (which we may or may not have personal experience with) and represent value for money, you should be aware that our opinions can differ.

A product we like and recommend may not be suitable for your unique goals. So always be sure to do your due diligence on any product before you purchase it.