How Many Goldfish in a 10 Gallon Tank?

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Most of us have had a goldfish at some point in our lives. In fact, goldfish have been kept as pets for hundreds of years, and today there are over 200 different varieties to choose from. 

I love goldfish, and I’ve kept them for many years in both aquariums and ponds. There’s something captivating about their bright colors and different forms that never fails to please.

If you’re thinking of getting a few goldfish, you might be wondering how many goldfish can live in a 10-gallon tank. 

In theory, a 10-gallon tank is big enough to house a single fancy goldfish. However, I don’t recommend keeping one of these gregarious, social fishes all by itself. In fact, in some cities and countries, it’s illegal to keep one solitary goldfish for welfare reasons.

Of course, if you’re planning on upsizing the tank fairly quickly, you could keep a few very small juvenile goldfish in a 10-gallon aquarium.

To find out more about choosing the best tank size for goldfish and what a 10-gallon tank can be used for, read this guide!

How Many Goldfish Can Live in A 10-Gallon Tank?

Girl feeding goldfish

Goldfish are a freshwater fish species that originates from China. Depending on the variety, some of the slim-bodied goldfish types can grow to over a foot long. However, the average goldfish kept as a pet is only about 6-8 inches long.

While goldfish can technically survive in a small bowl, they will not thrive. A small bowl does not provide enough space for your goldfish to swim around and exercise. Poor water quality is also a common problem in small bowls since they do not have enough room for a filtration system.

A 10-gallon tank, on the other hand, is a much better option for goldfish. It provides enough space for the average goldfish to swim around and exercise. The larger tank size also gives you the ability to add a filtration system to help keep the water clean and healthy.

What Kind Of Goldfish Should Be Kept In 10-Gallon Tanks?

Generally speaking, 10-gallon tanks should be reserved for juvenile or small goldfish. They can also be used to house goldfish fry (baby goldfish) while they grow larger. It is just large enough that they will not be cramped, but small enough that it is easy to maintain and keep clean.

However, it is possible to keep one adult, average-sized goldfish in a 10-gallon tank. It is important to have a filtration system designed for a much larger aquarium and regular water changes if you want to do this.

How Many Goldfish Can Be Kept In A 10-Gallon Tank?

The number of goldfish that can be kept in a 10-gallon tank really depends on the size of the fish. If you are keeping goldfish fry or juvenile goldfish, you can usually keep 3-5 fish in a 10-gallon tank.

If you are keeping one adult fancy goldfish, you will need to have a much larger filtration system and do regular water changes to keep the water quality high. However, note that it’s illegal in some countries to keep one single goldfish, and we don’t recommend that you do it for welfare reasons.

A variety of factors influence the number of goldfish you can keep in a 10-gallon tank. We will discuss these factors in more depth below, but it is better to err on the side of caution and provide more space rather than less.

What Affects The Number Of Goldfish You Can Keep In A 10 Gallon Tank?

As we mentioned above, a few different factors will affect how many goldfish you can keep in a 10-gallon tank. These include:

Body Size

The body size of your goldfish will play a big role in how many fish you can keep in a 10-gallon tank. If you are keeping juvenile or small goldfish, you will be able to keep more fish in the tank than if you are keeping one adult fancy goldfish. This is because smaller fish produce less waste and require a smaller tank than larger fish.

Generally speaking, you should allocate about 1 gallon of water for each inch of fish. So, if you have a school of 1-inch juvenile goldfish, you will be able to house 10 fish in a 10-gallon tank. However, if you have a single 6-inch fancy goldfish, you will only be able to keep one fish in the tank. All goldfish tank size calculations should err on the side of being conservative.

Goldfish Species

Ranchu goldfish

Did you know that there are over 200 types of goldfish? While each variety of goldfish comes from the same species, they have been bred over time to create a wide array of different shapes, sizes, and colors.

Some types of goldfish are more suitable for life in a 10-gallon tank than others. For example, larger goldfish breeds such as the Butterfly Tail Goldfish or a double-tailed goldfish like the Ryukin Goldfish are not well-suited for life in a small tank. These fish can grow over a foot long and require at least a 20-gallon tank to thrive.

On the other hand, smaller goldfish varieties such as the Comet Goldfish or the common goldfish are a better option for 10-gallon tanks. These fish only grow to be about 6-8 inches long and can live happily in a smaller space.

Filtration System

Another important factor to consider is the filtration system you use in your tank. A good filtration system will help to remove waste and toxins from the water, making it easier to maintain water quality. Ultimately, this will minimize your fish’s odds of bacterial infections and other illnesses.

care for a filter for an aquarium

Of course, frequent water changes should still be a crucial part of your goldfish care routine – especially if your tank only holds 10 gallons of water! All goldfish produce a lot of waste, so it is important to have a filtration system that can handle the load. We recommend using a filter designed for an aquarium that is twice the size of your 10-gallon tank.

A good filtration system will also include a biological filter. This type of filter uses healthy bacteria to convert waste into less harmful substances. A biological filter is an important part of any goldfish tank, but it is especially important in smaller tanks where water quality can decline quickly. This makes them a popular choice among seasoned goldfish enthusiasts.

Life Stage

There is a common misconception that goldfish babies and adult goldfish have the same needs. This could not be further from the truth! In fact, goldfish babies are some of the most delicate creatures.

Goldfish fry (baby goldfish) are born without any scales or fins. They are also very small, often measuring just a few millimeters in length. For these reasons, goldfish fry requires a smaller swimming space – in many instances, even goldfish bowls will do the trick.

On the other hand, adult goldfish need more space to swim and thrive. They also produce a lot more waste, requiring a larger tank with a more powerful filtration system. 

Special Considerations For 10-Gal Tanks

We’ve established that a 10-gallon tank is only ideal for goldfish under very specific circumstances. If you’ve decided that a 10-gallon tank is right for your goldfish, there are a few things you need to keep in mind:

Limited Decor Options

When it comes to decorating your tank, you will need to be mindful of your available space. Remember, the largest goldfish measures up to 1 foot in length, making every inch of space crucial – particularly in a smaller tank. This means that you won’t be able to put too many large decorations in your tank without taking up valuable swimming space.

Instead, focus on decor that is functional as well as aesthetically pleasing. For example, plastic plants are easy to maintain and can help to create a natural-looking environment for your fish. You can also opt for low-maintenance live plants, which can act as a fish filter and help to improve water quality.

Freshwater fish like goldfish also tend to enjoy hiding places. Unfortunately, there may not be room for caves or other elaborate hiding spots in a small space. Try these minimalist tank decor ideas on for size instead!

Possibility of Stunted Growth

A goldfish with a healthy life can expect to have a natural lifespan of 10-15 years. However, if your pet is living in a 10-gallon tank, goldfish growth will likely be stunted due to the growth-inhibiting hormones produced when fish feel cramped and stressed.

ranchu goldfish fry
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While a single goldfish can reach its full size in a 10-gallon tank, this is not the ideal situation for your fish. If you want to maximize goldfish growth, it is recommended to provide at least 20 gallons of space for each fish. Otherwise, your fish may never reach its full potential.

The good news is that even if your goldfish’s growth is stunted, it will still have a long and healthy life as long as you provide proper care. These are hardy fish known to adapt well to a variety of living conditions.

No Community Tank Option

If you’ve always dreamed about having a couple of goldfish living in your tank, know that a 10-gallon tank for goldfish will not accommodate this.

A common misconception about goldfish is that they NEED to be kept in groups. While it may be true that these are social fish that enjoy the company of others, they do not need to be kept in groups in order to thrive.

In fact, goldfish are perfectly content living solo as long as they have the proper care and attention. So, if 10 gallons is all the space you have available, focus on meeting the needs of a single goldfish rather than trying to cram multiple fish into a small space.


Of course, this rule does not apply to juvenile fish, which produce smaller bioloads. You can easily keep a pair of baby goldfish in a 10-gallon tank until they reach maturity.

RIsks of Compromised Immunity

Sick goldfish with bumbs on its scale, fish bowl pet

Even the hardiest fish can fall victim to disease if they are not properly cared for. One of the biggest risks of keeping goldfish in a small tank is that their immunity may be compromised, making them more susceptible to disease.

This is due to the close quarters in which they live and the fact that small tanks are more difficult to maintain. For example, it is easier for ammonia and other toxins to build up in a small space, putting even the hardy goldfish at risk. Raising healthy fish is considerably more difficult in a small tank.

In order to give your goldfish the best chance at a long and healthy life in a 10-gallon tank, you need to test your water regularly and take steps to keep the environment clean. This may include more frequent water changes as well as the use of a filter and/or air pump.

By taking proper care of your goldfish and its environment, you can help to ensure that your pet enjoys a long and healthy life, even in a small space.

The Takeaway

While a 10-gallon tank is not the ideal space for goldfish, keeping your fish healthy and happy in this limited space is possible. Juvenile goldfish and goldfish fry can also be kept in a 10-gallon tank until they reach maturity. At the end of the day, the most important thing is to provide proper care and attention to your fish. With the right setup and maintenance, you can help your goldfish thrive, regardless of the size of its home.

We hope you enjoyed this article and found it helpful. If you have any questions or would like to share your own experiences, please leave a comment below! And if you want to learn more about goldfish care, be sure to check out our other articles on the subject. Thanks for reading, and happy fishkeeping!

Wanda is a second-generation aquarist from the sunny tropics of Malaysia. She has been helping her father with his freshwater tanks since she was a toddler, and has fallen in love with the hobby ever since. A perpetual nomad, Wanda does her best to integrate fish-keeping with her lifestyle, and has taken care of fish in three different continents. She loves how it provides a nice break from the hustle and bustle of life.

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