Best Temperature To Keep Goldfish

Best Temperature To Keep Goldfish : Everything You Need To Know

Most people assume that goldfish prefer cold-water. This is generally true. However, there is much more information most people do not know about goldfish and temperature. In this post, I am going to share with you the best goldfish temperature range and everything else you need to know about goldfish and temperature.

The Best Temperature Range for Goldfish

So what is the best temperature range for goldfish? Well, the answer to this question could be pretty direct if there was only one breed of goldfish on the market. But there are many breeds. The two main ones are fancy goldfish and slim-bodied goldfish. 

Both of these goldfish breeds can survive in cold water. However, not both of them will thrive. 

The Best Temperature Range for Fancy Goldfish

Fancy goldfish are very popular. They are available in many aquarium pet shops. While they are probably more popular than their slim-bodied counterparts, they are also much more fragile. 

They are more fragile because they are extremely hybridized. The fact that they are extremely hybridized is responsible for their big eyes, big fins, and big heads. It is also responsible for their many health issues.

Since they are fragile, it is very important to maintain the temperature of your fish tank or bowl within the best temperature range for them. Because if you don’t, they will quickly start experiencing health issues and die. 

So what is the best temperature range for a fancy goldfish? It is between 78 and 82 °F. This is because studies show that it is at this temperature range that fancy goldfish thrive and grow the most. Moreover, this temperature is good for oxygenation and minimizes harmful bacteria.

In the United States and other Western countries, it is not very easy to maintain this temperature range. This is why it is important to acquire an aquarium heater. An aquarium heater can help you to maintain this temperature range and prevent day and night temperature fluctuations that can affect or stress your fish. 

You should only not buy an aquarium heater if you live in a city or region that is hot throughout the year. If you don’t, you should get a heater to protect your fancy goldfish from temperature fluctuations and cold winters. When you let the water in your fish tank get too low, it will increase harmful bacteria and stress the immune system of your delicate goldfish. And within weeks or months, this could kill your fish. 

So if you want your fancy goldfish to thrive, make sure you have a good aquarium heater. Or move to a warmer city or region. 

The Best Temperature Range for Slim-bodied Goldfish

Slim-bodied goldfish are the slim ones. They include breeds such as shubunkins, comets, and commons. They are not as popular as the fancy goldfish breeds but they are certainly less fragile. In fact, they are not at all fragile – they are hardy.

According to many experiments and studies, they live much better in outdoor ponds compared to the delicate fancy goldfish. They can also tolerate much colder temperatures even in aquariums compared to fancy goldfish. In short, they are the true cold-water goldfish.

The best temperature range for them is between 65 and 70 °F. Slim-bodied goldfish are known to thrive within this low-temperature range. 

They are also known to survive cold winters better than fancy goldfish.

So if you happen to have a slim-bodied goldfish, you probably do not really need an aquarium heater. This is unless you live in a place where it actually gets really cold.

What temperature is too warm for goldfish?

You now know the temperature range you should maintain for your goldfish. Now it is time to find out the hottest temperature your goldfish can handle. The temperature is 82°F. 

At this temperature, your goldfish starts getting really uncomfortable. Beyond this temperature, your goldfish will become stressed. This is why it is important to avoid situating your aquarium in a spot where it can be hit by direct sunlight as this can increase the temperature of the water inside it beyond 82°F.

It is also important to avoid placing your aquarium in front of a room heater or radiator for the same reason. 

What temperature is too cold for goldfish?

As stated in the introduction, goldfish are indeed cold-water fish. They can handle truly low temperatures. They can, in fact, survive at single-digit temperature levels. 

However, if you want your goldfish to grow and to enjoy life, you should maintain your aquarium temperature above 65°F. 

Issues with Wrong Temperature/ Sudden Temperature Changes

So what happens if you do not keep your goldfish within the right temperature range? Well, if you fail to maintain the best temperature range for your fancy or slim-bodied goldfish, you could kill them. It is that bad. 

If you are an experienced aquarist then you probably know that significant temperature changes can cause temperature shock to aquarium fish. If you are a beginner, this is something you should have in mind. And it is the reason why you should acquire an aquarium thermometer if you do not already have one.

It is also the reason why you should never do significant water changes especially if the water you are introducing has a significantly different temperature from the one in the tank.

A good aquarium thermometer will help you to constantly monitor the temperature of the water in your fish tank and to correct any sudden changes. In case the water temperature suddenly drops below the ideal temperature range or goes above it, it could result in effects such as:

  • Stress 
  • Swim bladder disease
  • Surface gulping 
  • Excess slime production 
  • Aimless floating
  • Lethargy
  • Rapid breathing 
  • Lack of motion

Simply put, things can get really bad for your goldfish when there is a sudden change in temperature. The effects above are danger signs that your fish is suffering. You need to take immediate action if you notice any of the signs.

The best action to take is to investigate the problem using your thermometer. If the thermometer shows that there has been a sudden change in temperature, do not rush to do a significant water change. You may be tempted to do this to return the temperature to the best temperature range for your goldfish but you should not.

This is because doing a significant water change will alter the temperature significantly and this will shock or stress your fish even further.

How to Remedy Sudden Temperature Changes

If you notice a sudden drop in temperature, the best way to bring back the temperature is to use an aquarium heater. The heater will gently warm your aquarium water and get it back to the range that is suitable for your goldfish without stressing it or them.

If you notice a sudden increase in temperature, the best way to lower the temperature is to use a fan or cold water bottles. A fan will gently cool your aquarium water to the ideal temperature range for your fish. Similarly, placing a cold water bottle inside your fish tank will also cool the water down. 

What You Probably Do Not Know About Sudden Temperature Changes

You now know that sudden temperature changes will shock and stress your fish. You also understand that this could be fatal. What you probably don’t know is that sudden temperature changes can also cause an invisible effect that could be far more damaging to your aquarium.

An effect that could kill your goldfish and even the next fish you introduce in your aquarium. 

The effect is the killing of your beneficial bacteria. Sudden temperature changes can harm and kill your beneficial bacteria. This will crash your tank’s cycle and prevent it from converting harmful fish waste products such as ammonia into harmless products.

The lack of conversion of ammonia will result in a gradual increase of the chemical to toxic levels. This could kill your goldfish and even the next fish you introduce unless you discover the problem and address it quickly.


As you can see above, there is a lot of information to keep in mind about goldfish temperature. The most important thing to note is that there are two popular breeds of goldfish and they have different ideal temperature ranges. Another important thing to note is that it is important to have a stable temperature to prevent your goldfish from being shocked or stressed. 

Lastly, you should know that sudden temperature changes can also negatively affect your beneficial bacteria leading to a surge of toxic ammonia in your fish tank. Therefore, you should do all that you can to maintain your fish tank water temperature at the ideal temperature range for your goldfish and to prevent sudden changes in temperature.