Do Goldfish Need A Heater? Will They Get To Cold

Goldfish are glamorous and good-looking aquarium fish. They are easy to keep in the aquarium and are generally peaceful. Goldfish are easy to care for because you can meet their demands easily; they are not strict with their tank and water requirements.

Goldfish are cold-water fish and they do not need a heater. You might only consider including a heater if the tank temperature is below the ideal range. In this case, the heater will function more in stabilizing the tank temperature than raising it. 

do goldfish need a heater

However, it is essential to note that different goldfish types might have a slight variation in their temperature demands. Slim-bodied goldfish type can tolerate temperature slightly below or above freezing points.

On the other hand, fancy goldfish cannot tolerate water temperatures below 550F. However, every type of goldfish needs to be in a stable tank with a suitable temperature.

What Temperature is Ideal for Goldfish?

Temperature is one of the crucial parameters in a goldfish tank. It is crucial to keep the goldfish’s tank’s temperature at an optimal temperature to guarantee their survival. A condition of too high or too low temperature might be dangerous or even kill your goldfish.

Goldfish are cold-water fish, and their temperature demand is quite variable. They can cope in a temperature range between the ranges of 50-750F. They can also cope with a temperature that is slightly above or below this range.

Since goldfish are cold-water fish, they do not need a heater. In fact, it is best to keep them away from external heat sources and radiators. You can only consider using a heater if you need to raise the tank’s temperature to a suitable level.

Goldfish might also find it hard to cope with a drastic temperature change in the tank. Likewise, ensure the tank’s temperature stability, and if you need to make any change, it is best to make it gradual.

How Can I Test the Tank Temperature?

Testing the temperature in the goldfish tank is essential to keep it within a suitable range. Likewise, you should ensure you are carrying out an accurate test for the safety of your goldfish.

You can’t check the temperature of a tank by mere physical evaluation. It would be best if you used the right tool for adequate measurement. The best way to check the temperature of the tank is to use an aquarium thermometer.

All you need to do is strategically dip the thermometer in the tank and wait for a few seconds for it to read the temperature appropriately. The best positioning for your thermometer is somewhere above the gravel line.

If you are using a heater in the tank, it is best to place the thermometer at the opposite end of the heater for accurate measurement. Both floating and standing thermometers can go down in the aquarium for precise measurement.

Do Fantail Goldfish Need A Heater?

Fantail goldfish is one of the most common types of goldfish in the aquarium. Unlike tropical species, fantail goldfish prefer colder temperatures in their tanks. Therefore, there is no need to include a heater in the fantail goldfish’s tank.

You can only consider using a heater to stabilize their tank temperature if the room temperature drops below the freezing point. Or you are keeping your goldfish outdoors where the temperature is below the standard demand.

Where Do I Set Up A Heater?

Setting up your tank heater inappropriately is as good as not using a heater at all. In some cases, it is even more dangerous. The heat will not be evenly distributed through the tank and will eventually not serve its purpose.

There are different types of heaters and the size to choose is dependent on the size of your fish tank. Similarly, the heater’s positioning is essential for the overall effectiveness of the heater in the tank.

The best place to position your heater is near the filter outlet/inlet or near a circulation pump to ensure even heat distribution.

If you are using a submersible aquarium heater, it is best to position it horizontally near the bottom of the tank. You can also place it vertically, depending on the size of the tank and your preference. The positioning will determine if the heat will be evenly distributed or not.

Do Goldfish Need A Heater In Winter?

Keeping your goldfish during winter requires diligence. The question of goldfish needing a heater during winter or not is dependent on several factors.

If you are keeping your goldfish outdoors during winter, you might need to include a heater. The temperature outdoors during winter might drop below an appropriate point for goldfish in most areas.

On the contrary, common goldfish will not necessarily need a heater during winter if the tank is indoors. They can still cope with a temperature that is slightly below the normal range.

However, fancy goldfish will need a heater during winter because they are more vulnerable. They are usually prone to infections in temperatures below 60°F. The heater will help them stabilize the tank temperature and keep it optimal for the fish’s safety.

What Temperature Is Too Cold for Goldfish?

Goldfish are generally cold-water fish. Even though they can cope with variable temperatures, they might find it hard to survive in a tank where the water is either too hot or too cold. Any temperature below 600F is considered too cold for goldfish.

At this temperature, goldfish become sluggish, and the fish’s metabolism slows down. Likewise, goldfish will lose their appetite, and they will become lethargic and vulnerable to diseases and infections.

Can Goldfish Stay Outside In Winter?

The outdoor temperature during winter might become unfavorable for goldfish because it might drop below the freezing point. Therefore letting your goldfish stay outside during winter requires diligence and extreme care.

Goldfish can stay outside during winter if you include a heater in their tank. The heater will raise the tank temperature to a suitable level and stabilize it.

Alternatively, goldfish can survive outside during winter, significantly below freezing point by going into hibernation. However, goldfish in hibernation needs plenty of oxygen. Likewise, it is essential to keep ice off the tank or pond.

Can Cold-water Kill A Goldfish?

Goldfish are cold-water fish that can even survive in winter. They can cope in cold lakes, streams, and rivers. However, goldfish being cold-water fish do not mean that they can stay in frigid and freezing temperatures.

So, yes, cold can kill goldfish when it becomes very unbearable for them. When water temperature becomes too cold, their metabolism slows down, they stop eating, and become lethargic.

They will also become vulnerable to diseases and infections. Consequently, these conditions might force goldfish to go into hibernation or eventually die off.

How Often Should I Feed My Outdoor Goldfish In Winter?

Proper feeding is one of the essentials of life. The food you feed your goldfish during specific periods will determine how well they will cope with the situation.

It is expected that the temperature outdoors will drop during winter. When the water temperature outdoors during spring is in the range of 50-600F, you should reduce goldfish’s feeding to 1-2 times a day.

When the temperature drops below 500F, it is best to stop feeding the goldfish. At this temperature, the metabolism of the goldfish will drastically reduce, and the food might not even be useful for them.

At this temperature, the goldfish will lose appetite, become inactive, and consequently, they will stop eating. Therefore, stocking your goldfish’s tank with food at this point will do more harm than good. They won’t eat the food, and it will only liter the tank and make it more uncomfortable for them.

Frequently Asked Questions 

Here are some frequently asked questions about adding a heater to a goldfish tank;

What happens if I overheat the tank?

Water temperature is one of the essential parameters in any fish tank, and goldfish is not an exception. Goldfish are cold-water fish, and overheating the tank will make the tank uncomfortable for them.

If you overheat the goldfish tank, the oxygen level will start to deplete. Low oxygen levels will make the fish suffer from general exhaustion and stress. It might weaken the immune system of goldfish and make them lose basic body functionality. So, it is safe to say overheating the tank can lead to the death of goldfish.

How long should I heat an aquarium?

Heating your aquarium to a suitable temperature is a good idea, but overheating the tank can be dangerous. You should heat your tank for about 24-48 hours. Ordinarily, an aquarium will reach the desired temperature within the first 24 hours, but the extra hours will ensure the temperature’s stability. You can continuously use a suitable aquarium thermometer to follow up the temperature in the tank to avoid overheating.


Goldfish is a loveable cold-water fish that can cope at varying temperatures. You won’t have to include a heater in the tank because they love cold water. A heater might only be necessary during winter outdoors or situations where you need to raise the tank’s temperature to a suitable temperature.