I get commissions for purchases made through links in this post. Learn more.

Do Goldfish need a Heater?

Most aquarium owners strive to make their tanks as comfortable as possible for their beloved fish. In fact, tanks work best as aesthetically pleasing features and vibrant ecosystems when they recreate the natural environment of the tank inhabitants.

This means getting a lot of different things right. For example, the water conditions and chemistry have to be just right to allow all living creatures, from the goldfish to the coral, to survive and thrive.

What’s more, you need to make sure that the species in the tank are all compatible, the filtration is adequate to keep your tank healthy, and the environment is sufficiently well lit and stimulating.

One of the things that a lot of tank owners worry about is the temperature of the tank water. This can have a dramatic impact on the health and general well-being of your precious goldfish.

So, if you want to find out once and for all do goldfish need a heater, and what is the optimum heat conditions for these fish, then you’ve come to the right place.

What Conditions do Goldfish Live in the Wild?

Goldfish have been domesticated now for many thousands of years, from the ancient Chinese empire onward. As a result, the domestic varieties found in aquariums all over the world differ significantly from their cousins in the wild.

7 Types Of Aquarium Algae
7 Types Of Aquarium Algae

The goldfish is a member of the carp family, and it is a relatively hardy little fish that can survive a wide range of conditions. This doesn’t just mean temperatures, it can also live in waters of varying hardness, and pH, and can tolerate sometimes large swings.

It is a freshwater fish that is native to streams and rivers of East Asia, and as a general rule it is used to cold waters.

What is the Optimum Temperature for Goldfish?

Whether or not you will require a heater for your goldfish is dependent on the local climate of your area. This of course means what is the average temperature, but you also need to consider whether the location of your tank is subject to large seasonal changes in temperature. This needs to be considered relative to the optimum temperatures that goldfish like.

Most goldfish are suited to cold waters at a temperature that is comfortable for humans.

The optimum range is between 20 and 22 degrees centigrade, but they will not suffer too much if the temperature strays slightly above or below these values. This is standard room temperature conditions.

If your tank stays at around this temperature all year round then the good news is that you probably won’t require a heater. If the temperature commonly drops to the low teens then a good tank heater, rated for your tank size, is probably a good investment.

Rapid Changes in Temperature

Heaters can be useful if thermostatically set to keep the water at a constant temperature. This is because rapid changes in temperature can do great damage to some types of goldfish.

Temperature swings are especially dangerous to smaller or undeveloped fish, who could be wiped out overnight. For any tank owner in a colder climate, who wants to avoid such a nightmarish scene, they should definitely seriously consider a heater.

Changing the tank water can also provoke rapid temperature changes in a tank. As a result, this operation should be completed gradually and with great care.

If your tank water is heated then you should heat the new tank water to the same level before introducing it to the tank.

So, to answer the question do goldfish need a heater, you need to consider your own personal circumstances. Is the location of your tank naturally cold or subject to severe temperature fluctuations?

What are the Benefits of Installing a Heater?

If you do decide to install a heater, you can be assured they will bring some direct and indirect benefits. Of course, the most obvious advantage is that you can set them to keep a steady and stable temperature for your tank water, and then you can rest assured that your goldfish will thrive even in the most trying weather conditions.

Decrease of Bad Bacteria

The other main advantage of heating your tank water is that it can reduce the level of bad bacteria present in your tank. The distinction between bad bacteria and good bacteria is a very important one for aquarium enthusiasts.

Some bacteria is very necessary because they underpin the nitrogen cycle that helps to keep your tank clean and clear, and the ecosystem flourishing. This ‘good’ bacteria consumes the waste that fish and other living creatures naturally produce, which would become toxic otherwise, and thereby help lower the level of ammonia and nitrite in the water.

On the other hand, ‘bad’ bacteria can cause disease or illness in your fish, or can attack other elements of the ecosystem, and cause indirect damage to your goldfish that way.

Extensive studies have shown these types of bad bacteria do not do well in warmer waters. So, by heating your tank you could have a long-lasting positive impact on the health and well-being of your goldfish.

Furthermore, so long as you do not heat your tank to unreasonable levels (e.g. more than 28 C) the level of dissolved oxygen in the water is still enough to support a thriving aquatic community.

Dissolved oxygen is the life blood of your ecosystem, and it decreases as the solubility of oxygen in water decreases with increasing temperature, so you must exercise caution.

Growth in Your Fish

The other often quoted benefit of using a heater to achieve warmer waters is that higher temperatures promote maximum growth in your fish. This is because high temperatures increase your fish’s immune system, allowing them to process more calories and thereby grow at an accelerated rate.

This is most important when your fish are young (to grow them to maturity) or when you would like to accelerate breeding in your goldfish tank.

Of course, in such cases the heated water is best combined with a protein heavy and calorific diet.

Do all Goldfish Require a Heater?

Not all goldfish are created equal. While some species are very hardy critters who can survive in waters approaching freezing, other types of goldfish are very susceptible to illness in cooler waters.

It is important that you know what kind of goldfish you have and what the specific requirements for that type are. If in doubt consult an expert or your local pet store.


As a general rule, pond goldfish will not require a heater. These are hardy fish well used to seasonal lows and can adjust their patterns accordingly.

For example, pond goldfish can lower their metabolism and almost hibernate during the winter to deal with the much lower temperatures.

However, on the other end of the spectrum, there are many types of goldfish who greatly dislike colder waters and will suffer if kept in it for too long. In general, fancier breeds of goldfish, which are more rare and expensive, are less tolerant of colder conditions.

This includes, but is not limited to, goldfish like phoenix goldfish, fantail, goldfish, lionheads and orandas. Many of these types of goldfish are very aesthetically pleasing breeds, with vivid colors and playful personalities, but if you own them, they may require a heater.

Their immune systems can become very compromised in colder waters, meaning they are susceptible to common illnesses that they would usually be able to fight off.

So the answer to the question; do goldfish need a heater, is that is depends on the goldfish.

Tips and Tricks


Video: “Aquarium heaters complete guide – all you need to know about fish tank heater”


If you do decide to install a heater in your tank there are some important guidelines that you should follow.

First of all, you need to recognize that overheating the tank water could be disastrous. Never allow the temperature in your tank to approach or exceed 30 C.

At this temperature the level of dissolved oxygen can become so low that it cannot support the ecosystem and your fish could quickly die through lack of oxygen.

Also, in the summer it might be more important to have the ability to cool your tank rather than heating it. If tank waters become uncomfortably hot you should have a means to reduce the temperature.

For example, you should consider adding more shade in the summer or installing a fan to cool the air temperature in the room.

Recognize that heating your tank could be expensive, especially if you have a large tank. Keep an eye on your electricity bills to track the running costs of your fancy heated aquarium.

Conclusion

Do goldfish need a heater?

This is a very important question for the modern tank owner. In general goldfish are cold water fish, but this does not mean that they will never need a heater. If your tank is in a very cold location or suffers from large temperature fluctuations, then you should definitely consider installing a heater.

There are other side benefits to installing a heater as well, such as reduced levels of bad bacteria and parasites, and increased growth. Outdoor pond goldfish do not require a heater, but fancy aquarium breeds might.

In the end this is a situation specific question that only you can answer.

Aqua Movement
Logo