What is the Best Temperature for Goldfish?

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The ideal goldfish water temperature is somewhat of a heated topic (pun completely intended). There’s a lot of confusion surrounding goldfish and water parameters. In the aquarium world, goldfish are known as sturdy cold-water fish.

It’s certainly true that this species is highly adaptable to low water temperatures.

But how low are we talking? Is colder water better? What about the ideal range? Don’t goldfish need a heater?

Don’t worry, I’m here to answer all these burning questions and more! Whether you’re a new goldfish keeper or are pondering moving your goldfish in a heated community aquarium, this article is for you!

I’ll cover everything you need to know, from the ideal water temperature for health, all the way to the optimal temperature for breeding your fish.

I’ll also touch on issues such as the heater, temperature shock, and absolute temperature limits. So, let’s get started!

Goldfish Ideal Water Temperature

Goldfish are considered cold water fish due to their sturdy nature. They can adapt to various water parameters, including very cold water. But they can also live in slightly warmer water.

There’s quite a range when it comes to temperature. But neither end of the scale is ideal.

The optimal temperature range for goldfish is actually quite narrow. The numbers differ slightly depending on the strain of goldfish you keep. But in general, you should aim for 68-74˚F.

This range means the temperature is high enough to keep your fish healthy and active. A higher temperature encourages growth and appetite.

Lower temperatures tend to slow metabolism and increase lifespan. But goldfish kept in low temperatures won’t reach their full growth potential. Keep in mind these ranges apply to common goldfish types.

Certain species, such as Shubunkins, Comet, and Calico Telescope Eye goldfish prefer slightly lower temperatures, somewhere around 60-70˚F.

Do Goldfish Need a Heater?

Goldfish can be kept in heated aquariums. But they don’t necessarily need a heater. Most goldfish strains can live happy, healthy lives in temperatures as low as 64˚F.

As long as your room temperature doesn’t drop any lower than that, you could safely keep the goldfish in a heater-free tank.

All this being said, I still recommend a heater for a few reasons. First of all, I would advise you to aim for a higher temperature, around 68-70°F.

This is ideal if you want your goldfish to reach a larger size and to breed more easily. Warmer water also encourages your goldfish to stay active.

If the water temperature is below 68°F, a heater becomes necessary. Secondly, a heater is crucial for keeping the water temperature at stable levels. I cannot stress how important this is.

Temperature fluctuations are damaging for your fish, and can even cause sudden death if the fish go into shock.

Goldfish Temperature Shock Symptoms

Sudden temperature fluctuations can induce a dangerous response in goldfish. This state is called “temperature shock” and it requires immediate attention.

The bad part is that the water temperature doesn’t even have to fluctuate by that much. A change of as little as 2 degrees is enough to cause issues.

The most common symptoms of temperature shock include lethargy, fish sitting at the bottom of the tank, buoyancy problems, excessive mucus production, rapid breathing, or fish gulping air at the surface of the aquarium.

Not fun! If left untreated, temperature shock can lead to irreversible damage or even death.

This is why you might want to think twice about skipping the heater. Even in a warm climate, temperatures can fluctuate quite a lot between day and nighttime.

Even if the aquarium temperature fluctuates within the ideal range, the fish can still experience temperature shock due to the abrupt change in parameters.

What Temperature is Too Cold for Goldfish?

Goldfish are quite adaptable to cold water. As long as the temperature stays slightly above freezing level, around 39°F, goldfish can survive.

But remember, goldfish, like all other fish, are cold-blooded creatures. A very low water temperature, although manageable, is far from ideal.

When the temperature drops below 65°F, your goldfish might become sluggish. This is due to a metabolic adaptation to the cold. Because goldfish can’t generate their own body heat, they must slow down their metabolism to survive in cold water.

This leads to slower or stunted growth and might stop your goldfish from breeding altogether.

Other than that, your fish won’t die when exposed to cold water above 39°F. But the transition must happen slowly.

Suddenly putting your goldfish in a cold-water aquarium or pond can still send them into shock and sudden death.

What Temperature is Too Hot for Goldfish?

Goldfish can’t stay healthy in water that surpasses 80°F. This is the critical upper limit. When the temperature climbs this high, goldfish start feeling stressed and lethargic.

Part of the reason is due to lower oxygen levels. The warmer the water, the lower the oxygen concentration.

An overheating goldfish will begin suffocating and showing the tell-tale symptoms of temperature shock. The most obvious sign is goldfish coming up to the surface to gasp for air.

Putting goldfish in water that’s too warm can cause sudden death in the worst-case scenario. If your fish survive, there are also some long-term health issues to be aware of.

Goldfish become vulnerable to parasitic infections, fungi, and various diseases when exposed to warm water, especially if this happens repeatedly.

To prevent the aquarium from overheating, place it in a dim-lit spot away from radiators, windows, or other light or heat sources.

What is the Best Temperature for Breeding Goldfish?

There’s not one single ideal temperature for breeding goldfish. It’s a bit more complicated than that.

That’s because goldfish are seasonal breeders. You’ll need to replicate the seasonal shifts in temperature in your home aquarium. This is the best way to encourage your goldfish to breed.

It sounds complicated, but it’s actually pretty simple. All you need is a heater and some time on your hands. You shouldn’t keep a steady temperature year-round. Instead, you’ll just change the temperature to mimic the natural fluctuations a fish might experience in the wild.

In a natural habitat, goldfish start breeding in early spring, once the temperature begins to rise back up after winter.

First, you’ll have to simulate the winter environment by lowering the water temperature to 54°F. Remember to let the temperature drop gradually.

You can keep the temperature around 54°F for a couple of weeks to a few months, depending on how often you want your goldfish to breed.

When you want to encourage them to lay eggs, it’s time to raise the temperatures back again. Gradually bring the temperature up to 68-74°F and see the magic happen!


To reiterate, goldfish can adapt to very low water temperatures. They can survive in temperatures as low as 39°F. But the ideal range for optimal growth and energy levels is 68-74˚F.

Most goldfish species will thrive with these parameters.

The temperature should never reach 80°F. Temperatures around this level lead to lower oxygen concentrations and can shock your goldfish. In all cases, the temperature should always be kept constant.

Sudden fluctuations can cause acute and long-term symptoms. They can even result in death. Using a heater is the best way to maintain stable aquarium parameters.

A programmable heater can also help you imitate natural seasonal changes to encourage breeding.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
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