Do Goldfish Need a Heater? Ideal Tank Temperature (2024 Guide)

goldfish in the aquarium water close up
Dr. Mollie Newton
Published by Dr. Mollie Newton PHD| Senior Editor
Last updated: May 7, 2024
Review Process and Evaluation Criteria
We conduct hands-on testing for all the products highlighted in our reviews and guides. Through anonymous product ordering and involving an independent team of testers, we gather direct experience to offer recommendations backed by data.

Establishing a new home for your ornamental goldfish can bring about numerous inquiries and obstacles. The most significant hurdles for some could be understanding the particular requirements of their goldfish, including their preferred food, optimal temperature, surroundings, plant life, and potential tank mates like betta fish. Remember that every fish possesses a distinct set of needs to fabricate the prime living circumstances for their prospering.

If this sounds like something that you’ve been facing with your home goldfish aquarium, worry no longer! We’ve gathered all of the necessary info for you in one helpful location, so follow along as we answer the question “do goldfish need a heater?”

Article Summary

  • Whether goldfish need a heater depends on various factors, including the goldfish variety, tank size, tank placement, and local temperature conditions
  • Outdoor ponds may require heaters in regions where temperatures frequently dip below freezing, as goldfish can tolerate cold temperatures to some extent.
  • When installing a heater, it’s essential to transition gradually to avoid shocking the goldfish.

Do You Need a Heater For Goldfish?

Goldfish at a Corner of a Fish Tank
Goldfish at a Corner of a Fish Tank

The short answer to this is that some, but not all goldfish will need a heater to reach the right temperature for them. It’s therefore important to know which goldfish variety you have in order to best meet their needs regarding the use of a heating element.

Most common goldfish you see at the pet store will likely not require a heater, provided that there is a filtration system and the water quality in the tank is kept at a safe level.


Regarding water quality in the tank, remember that sources of harmful chemicals such as leftover food, fish waste, and dead fish can all lead to dangerously high levels of ammonia which can cause toxic shock in your fish. As such, try to remove these as often as possible!

Another key factor to look at when choosing a heater is the amount of available oxygen within your tank. One that with too high a temperature has oxygen levels that are too low while simultaneously causing harmful bacteria and algae to thrive, meaning a heater can cause more harm than good.

Things to Consider

There are several key components to keep in mind when looking at whether or not you need to consider an aquarium heater for your goldfish tank setup.

As a rule of thumb, we highly suggest using a digital thermometer to keep track of the temperature in the aquarium, along with generally monitoring oxygen levels and water quality on a regular basis.

Temperature Change

If your tank has external factors that can influence the water temperature, this can cause swings in the overall comfort of your aquarium water for your fancy goldfish.

Having direct sunlight can lead to higher water temperatures, while being placed in the outside with additional water flows can cause rapid shifts throughout the season meaning cold water in the winter and warmer water in the hot months.

The goal for your aquarium should be to maintain a constant temperature, which can potentially mean a heated tank in addition to aquarium heaters if your tank is situated in a particularly freezing cold room. A heater may not be required if goldfish are the only species in your tank.

Tank Size

Small Goldfish Aquarium

While the tank volume is not a huge factor with regards to a heater, the larger surface area of some large tanks can mean additional heating requirements when facing low temperatures.

There can be a mild temperature range between the top and bottom of your goldfish tank, which can be remedied with the use of an air pump or a bubbler.

A tank with a smaller surface area, such as the typical goldfish bowl may be much easier to keep evenly heated and will likely not require the use of submersible heaters when properly positioned.

Thoughtful tank placement can make an indoor aquarium even easier for keeping your goldfish indoors.

Air pumps have the added benefit of providing additional gas exchange, which may be needed to maintain adequate amounts of oxygen in a heated tank.

Goldfish Breed

There are several different breeds of common goldfish that goldfish owners have to choose from when setting up their tank, and many are actually considered to be cold water fish.

These have different needs in terms of water temperature that are important to take into consideration when looking at a heater.

All goldfish are members of the carp family and are therefore typically considered temperate rather than cold water fish, but some have been bred to respond well to a higher water temperature.


Hardier varieties such as the phoenix goldfish, fancy goldfish, and common slim bodied goldfish can handle a colder temperature and may not require any additional heating at all, depending on the normal tank temperature in your aquarium.

These fish prefer between 60-70 degrees.

Like the betta fish of Southeast Asia, some goldfish breeds including the fantail goldfish, Tamasaba goldfish, and bubble eye fish are considered to be more tropical fish and prefer a higher tank temperature.

For these fish, a tank heater may be useful in keeping the temperature at a warmer 60-75 degrees Fahrenheit since some are extremely sensitive.

What Temperature Does a Goldfish Need?

Goldfish Swimming Towards Aquarium Surface
Goldfish Swimming Towards Aquarium Surface

In general, goldfish thrive with a water temperature between 60 and 70 degrees Fahrenheit. Anywhere above or below this desired range can lead to potential problems, depending on the breed.

Remember, your fish will primarily respond to temperature changes and prefer things to be comfortable and consistent in their goldfish tanks throughout the year.

What If The Water Gets Too Hot?

When considering the ideal temperature while using a heater for goldfish keeping, rising temperatures can lead to serious problems or even death for your goldfish, not to mention any other fish or goldfish buddies in the tank!

Effects of High Temperatures

  • Activity Levels: As the temperature rises, you’ll see an initial increase in the activity level of your fancy goldfish as it expects a breeding season to be imminent. Higher temperatures mean it’s time to lay eggs. Continually raising temperatures will see this level drop, as the fish becomes lethargic and burnt-out.
  • Stress: Constant hyperarousal from an overactive heater will lead to increased stress for your goldfish, which can manifest in odd behaviors such as lethargy, swimming towards the top of the tank, to remaining completely still.
  • Feeding: At first you’ll see a marked rise in the metabolism of your fish with a heater present, as their body begins requiring more food. As temperatures continue to increase this will drop off as the fish can no longer keep up with its body’s demands. Remember to not starve your goldfish or overfeed your goldfish as it can cause constipation.
  • Oxygen: Warm conditions caused by a heater can mean less oxygen available in the tank, a dangerous situation for any fish.
  • Bacteria: If your goldfish needs a heater this can mean higher temps where bacteria can thrive, leading to a decreased immune system response and higher risk for potential illness and infection.

Do Goldfish Need a Heater in Winter?

Provided that you are keeping fancy goldfish indoors, your requirements around needing a heater in the winter are still the same as previously stated. If the temperature in the room is enough to keep the tank at a consistent 60-70 degrees, a heater may not be required.

If you find that you’re having difficulty providing warm water for your goldfish and things are too cold, you may need to reconsider this and provide a heater to maintain an adequate temperature for all of the fish in your aquarium.

How Cold is Too Cold for Goldfish?

Since most goldfish, including the popular fantail goldfish and the traditional comet goldfish, are considered cold water fish, most can tolerate a dip in temperature below the 60 degree threshold.

However, this should not be considered the safe operating temperature of the aquarium and will likely be too cold for the other species in the tank.

In some instances, goldfish can manage temperatures as low as 50 degrees, but this will likely lead to their metabolism slowing as they move into a winter hibernation state.

As temperatures rise again in the spring and any ice melts, you should see the activity rate of your fish return to its normal levels.

Do My Goldfish Outdoor Pond Need a Heater?

If keeping your fish in an outdoor pond instead of a typical goldfish tank, you may want to consider a heater.

Depending on where you live, an outdoor environment can prove to be a particularly challenging habitat and will often require a heater if the temperature often dips below freezing temperature ranges.

Since these fish can manage cold temperatures, even if the surface of your pond freezes over they may be just fine and go into a hibernation state.

Here’s an interesting video about how goldfish do in a pond during winter.

Can goldfish and koi survive a cold Winter in a frozen pond without protection

Outside setups such as ponds can benefit from a pond heater when trying to keep water warm for fish other than just outdoor goldfish as temperatures fall throughout the seasons.

These function as a form of submersible heater, providing warm water and keeping those temperature changes to a minimum.

Again, consider breed and natural environmental water temperature when looking at the ideal temperature for goldfish kept outside in cold water.


If you have other species besides goldfish that are more sensitive to lower temperatures, think of adding a heater to your outdoor pond.

How Can I Adjust My Goldfish Tank Temperature?

When installing a heater in a goldfish tank, it’s important to remember to take things in steps, rather than immediately ramping up the heat.

The shock of transitioning from cold water to a warmer temperature can be a lot for your goldfish to take and cause shock, potentially damaging their health or causing them to behave erratically.

Most fish keeping heaters will come with a blue indicator light that will flash to let you know that everything is working properly. If you don’t see the light, turn it off and make sure that everything is properly installed before continuing.

Many heaters come with suction cups meant to hold it onto the side of the tank, make sure that these work by allowing it to sit for several minutes before actually turning on the heating unit.

After you’re sure that it will stick, you’re free to adjust the temperature to the desired level.


In today’s article, we answered the question “Do goldfish need a heater?”

The answer that we’ve found is that in some circumstances, such as if your tank is positioned in a place with an inconsistent water temperature (such as outside or by a drafty window,) you may indeed require a heater.

On the other hand, if you can maintain a consistent temperature of around 60-70 degrees, you can likely get away without an aquarium heater.

As always we appreciate you reading through this article on how to care for your fancy goldfish, we hope that it helped you along your aquarium journey and please feel free to share with any other fish fanciers you may know!

You May Also Like