Do Goldfish Need A Heater?

If you’ve ever kept fish as pets before, then you know that many of them need a heater. If you’re considering buying goldfish, you’ll be wondering, do goldfish need a heater?

What temperature should you keep your goldfish’s water? Is any temperature too cold for them? At what point should you install a heater? Keep reading to find out.

Do Goldfish Need A Heater?

The short answer is “no”, goldfish don’t need a heater. They are coldwater fish. If you keep your goldfish’s tank too warm, they may actually suffer.

Still, this answer does not apply to all scenarios. Does your house become very cold over the winter months? Or, do you keep your goldfish outside over winter? If you do, you’ll likely need a heater.

Goldfish Are Coldwater Fish

The perfect temperature for your goldfish is between 65-74°F. It’s very easy to maintain this temperature year-round if the goldfish live in an indoor aquarium. Most people keep their homes somewhere between 68-72 °F, so this is great for goldfish.

Some goldfish, like the shubunkins and comets, are especially cold-hardy. They’re ideal temperatures drop as low as 60 °F, and they can withstand the extreme cold much more easily.

Goldfish are also very versatile. While 65-74 °F is their ideal range, they can survive outside those ranges as well. Few fish are as adaptable as goldfish when it comes to temperature changes. Although they might not be happy about it, they can live in both overly warm and cold temperatures.

This is more true for outdoor pond-type goldfish than fancy goldfish. Fancy goldfish are not adapted as well for the cold. Really, it’s not ideal to place them in an outdoor pond at all, it’s better to keep them in an indoor aquarium.

For fancy goldfish, you shouldn’t let the temperature get below 65 °F. If it drops slightly below that, your fish isn’t likely to die, but they may become sick.

Fancy goldfish that are less cold tolerant include:

What Happens If The Water Is Too Warm?

Once the temperature reaches above 75 °F, your goldfish’s metabolism slows down. Water that is too warm can stunt your fish’s growth. It also compromises their immune system and leaves them more susceptible to disease.

In pond fish, you can only control the temperature of the water so much. It’s best to build your pond in a shady location so that the water doesn’t become too warm. Ideally, the water will not rise above 80 °F.

Water doesn’t retain as much heat as air. It also heats up more slowly. So, if you keep your pond shaded, it’s unlikely that the water will rise to dangerous temperatures.

76-86 °F is the ideal temperature for young, growing fish. It may slow an adult’s growth slightly, but it won’t have an extreme effect on them. You should continue to feed your fish 2-3 times a day.

At 87-97 °F, growth will slow for both adults and juveniles. You shouldn’t feed more than two times a day.

98-100 °F is the absolute hottest your goldfish can handle. Their growth will be significantly slowed. Their immune system may also be severely compromised. You should only feed them 1-2 times a day.

Goldfish are not likely to handle temperatures above 100 °F.

Plus, water that rises above 80 °F can become dangerous for your goldfish. The warmer the water, the less oxygen is present. Goldfish need lots of oxygen. They will become stressed, and may even become sick if they don’t have access to enough oxygen.

Can You Keep Goldfish In A Warm-Water Tank?

Many people love goldfish, but they want a bit more variety. So, they consider adding a goldfish to their tropical fish tank. The problem with this is that most tropical fish need a temperature of about 78 °F.

Yes, goldfish can live in temperatures that warm, but it’s not ideal. They won’t be as happy and their metabolism will slow down. Plus, their immune system will become compromised.

So, you’ll be sacrificing the happiness of your goldfish to keep your tropical fish happy. Likewise, if you remove the heater, you’ll sacrifice the well-being of your tropical fish for your goldfish.

There are some cold-water species that you can house with goldfish. Overall, though, it’s best to keep goldfish with other goldfish.

What About Wintertime?

Goldfish that live outside during the wintertime may need a heater. Goldfish can survive extreme temperatures. But, they may die in freezing temperatures without adequate oxygen.

If your house drops below 65 °F during the wintertime, you’ll also want to get your fish a heater.

The ideal temperature for goldfish is between 65-75 °F. This is the perfect temperature for breeding, and it’s the temperature at which your fish will be most active.

As the temperature drops, your fish will become less active. At 55-64 °F, goldfish slow down and begin to prepare for hibernation. This is when you should cut their feedings down to once a day.

At 44-45 °F, goldfish are in a state of partial hibernation and should not be fed. Between 32-43 °F, goldfish are in complete hibernation and still should not be fed.

It can be hard to keep goldfish alive in freezing temperatures. If you live somewhere where the temperature drops below freezing, buy a pond heater!

Although goldfish can survive in these cold temperatures, it’s not ideal. To keep your goldfish happy, the temperature shouldn’t drop below 65°F.

Fortunately, there is an easy solution. You can buy an electric pond heater to go into your pond.

What Kinds Of Heaters Are There?

There are three basic kinds of heaters available. Whichever you choose depends on which will work best for your situation.

For 30-100 gallon aquariums, you might choose a submersible heater. These are one of the safest kinds of heaters. They’re also the easiest as they submerge completely underwater. All the heat transfers to the water without any being lost to the air.

Immersible heaters are similar, but they don’t go all the way in the water. The heating element goes in the water while the hardware stays above the water.

These are more affordable, but they’re also more dangerous. You have to watch that the water level doesn’t drop low enough to leave the heating element exposed. This can lead to overheating and a potential fire.

In-line heaters are going to be your best option for tanks and ponds above 100 gallons. The heating element sits outside the tank. The heat passes through a filter or pipe that enters the water.

You can also buy heaters that go in the substrate or in a sump. In-sump heaters are another good option for larger tanks and ponds.

How Do You Check Your Water Temperature?

Fortunately, it’s easy to check your water temperature. You simply need to place a thermometer in the aquarium and read the temperature every day.

You can also buy a heater that has a thermometer built in. These are more costly, but they’re very convenient.

If it’s cold and you do need to use a heater, checking the temperature is extra important. Although it’s rare, heaters can malfunction. At worst, the heater may get too hot and boil your fish. At best, the heater may die and leave your fish in too-cold temperatures.


Goldfish are coldwater fish that thrive in temperatures between 65-75 °F. As such, a heater is not usually necessary. But, if you keep your house very cold, or your fish live in outdoor ponds, you may need to consider getting a heater.

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