Goldfish water temperature: What temperature should goldfish water be?

In this article, we look at goldfish water temperature. What temperature should goldfish water be? And how does temperature affect your fish?

Goldfish are hardy fish that can survive a wide range of water conditions. This includes very cold and quite warm water.

However, there are still some temperatures that are better for goldfish than others.

So, if you’re going to take good care of your goldfish, you need to keep their tank water at a comfortable temperature.

Read on to find out:

  • What temperature goldfish water should be
  • How to measure your goldfish tank temperature
  • The right temperatures for breeding goldfish
  • And why air supply is so important in warm water.

What temperature should goldfish water be?

tank water temperature of between 20°C – 23°C (68 °F – 74°F) is an ideal temperature for goldfish.

This temperature will be high enough to encourage strong growth, but without being so high that your fish become stressed by hot water and low oxygen levels.

Stability is also very important. Goldfish don’t like sudden changes in temperature.

Unless you plan to breed your fish, you should keep your tank water temperature as stable as possible all year round.

Breeding tank temperature

The advice above assumes you aren’t attempting to breed your goldfish. If you are, you’ll need to manage your tank water temps a little differently.

Rather than maintaining a steady temperature all year round, you should try to replicate the temperature changes that occur in nature.

Goldfish spawn in the spring, when water temperatures rise after the cold winter.

To encourage your goldfish to lay eggs, you should lower the temperature of your tank in the winter. Gradually lowering the temperature to around 12°C / 54°F is ideal.

Then, when you want to induce breeding, gradually raise the temperature of your tank water to between 20°C – 23°C (68 °F – 74°F).

Find out more about breeding goldfish and baby goldfish.

Do goldfish need a heater?

Goldfish don’t always need a heater. They can live in such a wide range of temperatures (more on this later!) that they will survive quite happily without a heater in most home aquariums.

However, we’ve already talked about how some temperatures are better than others, and how you’ll need to vary your temperature in order to breed your fish.

If your water temperature is below 20°C (68 °F) we recommend buying a heater. Otherwise, your fish might not grow as well.

What temperature can goldfish live in?

What water temp is too hot for goldfish?

Your goldfish will become very stressed if kept in water that is warmer than 27°C / 80°F.

Avoid placing your tank in direct sunlight or near radiators so that your water temperature stays below this level.

The hotter your goldfish’s water gets, the less oxygen there is in the water.

Of course, goldfish need oxygen to live, so you must ensure that your tank has an adequate “aeration system” (a system of adding air into the water).

We recommend buying a tank that has a large surface area. Avoid “tall” tanks that have a poor surface area to volume ratio. And be sure to include an air pump in your setup.

What water temp is too cold for goldfish?

In terms of a minimum temperature, goldfish can survive in water that is close to freezing.

However, you should really keep your tank temperature above 18°C / 65°F (when not attempting to induce breeding) in order to encourage strong growth.

The most important thing is that your tank temperature does not change suddenly.

Sudden changes in water temperature can shock your goldfish and contribute to problems such as swim bladder disease.

Don’t forget your other fish

Remember – your goldfish tank water temp needs to be suitable not just for your goldfish, but for all other plants and animals living in your tank.

Tank water temperature is therefore one of the key considerations when choosing fish that can live with goldfish.

You’ll need to find a goldfish tank mate that enjoys a similar temperature range (as well as other similar conditions) to goldfish.

How to measure your goldfish water temp

To measure your tank temperature you will need to purchase an aquarium thermometer and follow the instructions.

There are three main types of aquarium thermometer:

  • Ones that stick to the inside your tank
  • Ones that stick to the outside of your tank
  • And digital thermometers

We’ve found that quality digital thermometers generally give the most accurate readings.

12 thoughts on “Goldfish water temperature: What temperature should goldfish water be?”

    • My tank temp is constantly 27oC . This is because the water pump is warm while running.is this ok. It’s about 15L tank

      Reply
      • Hi Cathal, thanks for your comment,
        27C is too warm for goldfish to live comfortably in, we normally recommend not to go over 25C at a maximum, 15 litres is also too small for goldfish as they can grow to about a foot long.
        Instead I would recommend something like harlequin rasbora, green neon tetras or cherry barbs, as they might fair better in the warm small tank.
        hope this helps.

        Reply
  1. Henry you also need a bigger tank mate, or less goldfish. Your tank is only big enough for 1 fancy… and definitely not suited to 5 fish

    Reply
  2. I currently don’t have a heater but am planning on getting one as the temperature in my fish’s tank is around 50 F- how much is gradually to get it to 70? Should it be a degree a day or slower/ faster ?

    Reply
    • This is a great question, that I would like to know the answer to as well. I had one large tank go from 65-69 degrees within an hour I think. Another smaller tank was 68 degrees that I brought up to 72 degrees in 1-2 hours. I hope my fish can withstand the changes and be better tomorrow.

      Reply
    • Hi Sandra, thanks for your comment,
      Different fish can tolerate different drops and rises in temperature, some fish species have an 10C temperature drop over night within the span of a couple hours in their natural environment.

      increasing temperature by 1 degree Celsius every hour or 2 should be enough to allow them to adjust, nearly all fish are used to this rate of temperature change.

      And I would highly recommend getting a heater, they are worth the small expense.

      hope this helps.

      Reply
  3. I have an 80 l tank. Just moved to s spain and need to know what sort of fish or reptiles i can have . Can get cold in winter and up to 40 in summer. The tank would b indoors for 2 months so as to seen. We have a/c but only when indoors. Would appreciate your advice

    Reply
    • Hi Marjorie,

      It can be difficult to keep fish or reptiles in a small tank outdoors like this. Keeping a small encased tank outdoors will cause it to become extremely hot and extremely cold too quickly, too quick for any fish or reptile to put up with.

      we may be able to recommend some smaller rice fish, danios or goldfish to keep out in late spring or summer, but they could not be permanent residents of the tank over the full year.

      As for reptiles, you may be able to keep horsefield tortoise or hermanns tortoises, but bare in mind they can live over 100 years an become extremely large.

      I Know that there is a wild population of hermanns tortoise in spain however, so you may need to check your local wildlife laws to see if you can legally keep them as pets.

      hope this helps

      Reply
  4. Hello.

    My daughter has 2 goldfish (approx. 5 in. each) & last week we upgraded to this 20 Gal. tank (https://www.petsmart.com/fish/tanks-aquariums-and-nets/aquariums/top-fin-led-bubble-wall-aquarium-kit-64706.html?cgid=300129&fmethod=Browse).

    We have a simple temperature stick that is suctioned to the inside of the tank & it is constantly around the 80° F mark. Do we need to lower the temperature? They seem to be swimming around just fine, but I want to make sure they are ok.

    Reply
    • Hi, thanks for your comment,

      we are glad to hear that you have upgraded the size of your fish tank and are taking the right steps to providing good care for them.
      80F is quite warm for goldfish.

      If you can, try to bring it down, you may do this by leaving the lid open (but be careful of the fish jumping) and or by adding a frozen water bottle and allowing it to float in the top of the tank.

      You can of course keep them at this temperature but it will speed up their metabolism, so they will need to eat more and may become more irritable and uncomfortable, which isn’t ideal for a tank as small as 20 gallons.
      Try to keep them at around 68F – 75F, they will be more comfortable, need less food and will produce less waste, making your life easier.

      hope this helps 🙂

      Reply

Leave a Comment