At the time of writing this, fall is just about upon us and winter will be here before you know it.

While normal people are thinking about Thanksgiving dinner and football…

… We fish people are thinking about our fish.

At least, you probably are, if you are reading this.

And probably not just thinking… worrying.

“How do I keep them safe until spring comes?”

“Will they even survive?”

Well good news:

Today’s post is going to discuss just that – how with proper attention, we can safely bring our goldfish through the winter to the other side.

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So when keeping goldfish outside in a pond during winter (or in some other outdoor freeze-proof container, like a large tub)…

There are some things to consider.


If you are fortunate to live in a tropical place that doesn’t get much (if any) snow or ice…

… Much of the below will be solved for you already.

But for the rest of us, we have to think about:

Preventing Total Freezing of the Water Surface

goldfish under ice

Image Credit: Herzstaub, Shutterstock

When that cold temperature hits and the surface of the water starts freezing, it’s really important to ensure there is an area for oxygen exchange to take place at the water surface.

How do you do this for ponds?

A pond deicer is generally the best option.

As long as the temperature does not go below freezing, you are generally good.

Preparing Tanks & Tubs

For outdoor or garage/greenhouse aquariums, a heater can be used.

Protected shelters are great because it protects the fish from more extreme weather…

… And often gives you a source of electricity.

A VERY nifty piece of equipment to have on hand is this baby:

What it does is it lest you regulate the temperature to be low without being too cold.

If you can’t get this…

You probably won’t find a regular aquarium heater that can be manually set to temperatures around 50F.

But one (or multiple, for larger tanks) heaters can be used to keep the temperature from getting too cold.

You can use a timer to turn the heaters on and off every 30 minutes so you don’t burn them out as fast and prevent things from getting too hot.

And you can adjust the timer settings depending on the period of weather you are dealing with (i.e. if it gets warmer for a while, reduce the time between when the heater kicks on).

This method generally results in temperatures that hover around 40-50F.

Again, it’s not as reliable and you can burn your heaters out.

You have to be careful and watch the temperature closely.

Wrapping the tank in insulation (styrofoam, bubble wrap or other insulator) is also a good idea.

This will help conserve the heat.

I would not advise using glass tanks at cold winter temperatures.

The glass can shatter if the temperature of the water is too different than the air around it.

Disastrous for your fish!


Use plastic or acrylic tubs or stock tanks.


It’s a good idea to have some kind of cover or lid.

Heat will escape primarily through the top.


There is no point in having a filter going at these low temperatures.

The biological filter basically dies below 60F.

So really all you need to worry about is aeration and water quality.

An airstone is usually a good idea.

If you have some sturdy cold-tolerant plants (such as hornwort), those might provide a bit of a water quality boost too.

Winter Feeding & Maintenance

Do not feed at temperatures below 50F as the digestive system shuts down, and fermenting food in the gut can harm the fish.

When the fish aren’t eating, water changes become unnecessary.

During a warm period, you may wish to let the water go over 50F and give them a bit of food.

Your fish will become very skinny as they lose all their excess fat.

Fun fact:

In hibernation, a goldfish produces its own alcohol in its blood to help it survive winter (source).

As far as water changes go…

… A monthly partial water change (usually a 25% vacuum) can be beneficial, but not always necessary.


Benefits of Winter to Goldfish

goldfish in frozen pond

Image Credit: Maleo, Shutterstock

Times of cold can be very beneficial for goldfish.

It helps them shed that excess fat they put on in the warmer months.

Overwintering goldfish outside can lead to a longer lifespan of the fish, provided they are hardy enough to withstand it.

It is as if the hibernation period pushes a pause on their life clock.


This period of cold helps induce spawning when it warms up in the spring.

Not to mention the last benefit:

It gives you a break from the strict care routine!

Fancy Goldfish Considerations

Should you have fancy goldfish…

… There are some special things to know.

For fancy goldfish, the temperature usually should not go below 45F or it can lead to swim bladder damage.

The longer the winter, the harder on the fish.

Ideally, letting the temperature stay above 55F is more gentle on the fish.

Don’t get me wrong:

Fancy goldfish like ranchus CAN go through winter.

It can just be risky, especially the colder and longer the winter is.


Fancy goldfish are more sensitive, they aren’t as hardy as your slim-bodied goldfish that are more physically adapted to enduring winter.

6-10 weeks generally is the recommended length to keep your fancy fish in hibernation.


Don’t let them get too cold!

Yes, they may survive it, but it can result in weakness that leads to subsequent infection when the winter is over.

Bringing fish out of hibernation should also be done slowly.

Drastic changes can be harmful and cause stress, shock and even death.

So keep change slow for the safest awakening of your goldies

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Winter doesn’t have to be stressful.

It can give you as a hobbyist the chance to relax, knowing your fish are being taken good care of.

When it comes time to wintering your goldfish, following the steps above can help keep your water babies safe and healthy.

I hope you enjoyed today’s post!