How Many Goldfish in a 10 Gallon Tank – 9 Things You Need To Know

Are you planning to get a goldfish but don’t know what size tank is best? Well, you’re in the right place to find out! You can keep one or two goldfish in a 10-gallon tank if they are small.

Goldfish are a beautiful and active fish you’ll love to have in your tank. But, there are a few considerations before settling on a 10-gallon fish tank for your pet goldfish.  

What is the age of your fish? Are they fancy or common goldfish? Are you planning on upgrading the tank in the next few months?

goldfish swimming

When looking for my first fish tank, I considered all these and learned that the bigger the fish tank, the better. Why? Because any pet fish needs space to grow, swim and play in their fish tank to remain healthy.

With goldfish growing up to 10-12 inches as an adult with adequate space, a 10-gallon tank might only be the minimum tank size these species need.

If you are a beginner aquarist wondering how many goldfish you can put in a 10-gallon tank, you can find out how many to get, how to maintain a 10-gallon tank, and any downsides you should be aware of in this article.

Is a 10-gallon Tank Enough For Goldfish?

Yes. A 10-gallon tank is enough for one goldfish, depending on the species. It might sound like too much, but you have to consider that you’ll add more equipment to the tank soon. 

Goldfish are native to East Asia, and some of these beautiful species grow to about 10 inches by the time they are adults. The general rule among most aquarists is 1 gallon of water per inch of fish. 

So to keep an adult goldfish in a 10-gallon tank, they should not grow to be bigger than 10 inches. If you’re keeping juvenile fish, you can put 2-5 goldfish in a 10-gallon tank before they start growing. 

If you want to keep a single goldfish in a 10-gallon tank, then it’s best to consider which species you’ll have. 

Below you can find the best goldfish species that can be happy in a 10- gallon fish tank. 

Types of Goldfish and Tank Size They Need

With over 300 species of goldfish, it can be hard to find out how big your goldfish will get and whether or not a 10-gallon tank will be enough. There are common, fancy, and single-finned goldfish, so choosing the right one for your tank needs research.

goldfish in 10 gallon tank

Most of these fish love swimming and need the space to do It. That’s why a 10- gallon tank is only the minimum tank size for some goldfish species that grow to over 10- inches long. 

10- gallon tanks are ideal for breeders because they can house baby goldfish before moving them to a larger tank. Fancy goldfish like Bubble eye and Pompon goldfish are suitable for this minimum tank size. 

Here are some goldfish species you can put in a 10-gallon tank according to their sizes : 

Goldfish SpeciesSize 
Bubble Eye4-6 inches 
PomPom4-6 inches 
Butterfly Tail4-8 inches
Tosakin4-8 inches 
Lionhead4-8 inches
Telescope8-10 inches
Oranda8-10 inches
Watonai10-12 inches
Feeder10-12 inches

Although a 10-gallon tank is enough for these small goldfish species, they can get lonely and bored if the tank isn’t stocked with decorations and plants. You also need to add tank equipment to maintain proper tank parameters. 

How to Maintain a 10 Gallon Tank For Goldfish

If you’ve decided to go with a 10-gallon tank for your goldfish, you need to consider everything from the type of filtration system to the lighting your goldfish needs. 

Before they outgrow the 10-gallon tank, here is how you can maintain it to ensure they are healthy and happy:

Test and Monitor the Water Parameters

With goldfish, you’ll need to maintain specific water parameters because they are freshwater fish that need warm waters. The water temperature should be between 68 °F – 74°F. These temperatures encourage the growth of healthy fish.

Goldfish also need treated water to survive. Using tap water will harm their small bodies because it contains chemicals like chlorine. An aquarium test kit will come In handy to help test the water parameters to ensure they are suitable for your pet goldfish.

Carry Out Regular Water Changes

The best way to ensure your fish tank is clean is by carrying out frequent water changes. A 10-gallon tank is smaller than the required tank size for goldfish, so it can quickly get dirty.

common goldfish

Uneaten food and waste in the tank can cause a build-up of chemicals like ammonia. Ammonia and nitrate build-up will make the tank unlivable for your goldfish.

Constant water changes will also help dilute the growth-inhibiting hormones in goldfish. So even if your goldfish is In a 10- gallon tank with good quality water, they can still keep growing.

Avoid Overfeeding Your Fish

The last thing you want to do is overfeed your goldfish. It’s not only unhealthy for them, but it can ruin the tank environment, which will affect your goldfish’s immunity. 

Feed your pet goldfish 2-3 times a day. If you’re worried this isn’t enough, you should know that these fish can even go 14 days without food. They’ll be okay with good water quality and snacks like algae to eat. 

Ensure you remove uneaten or leftover food from the bottom of the tank while cleaning. Doing this will keep the water healthy for your goldfish.

Control the Lighting In the Fish Tank

All fish, including freshwater species like goldfish, require light for their wellbeing and growth. You can use artificial light if you don’t have a setup that allows direct sunlight into your goldfish tank. 

Light also helps with your goldfish eye development, so you shouldn’t keep them in complete darkness. The lights shouldn’t be too bright either because that can cause your goldfish eye strain, and we want them to see you and any pellets dropping in their tank’s water.

If you find them hiding under filters or struggling to eat their food when you turn the lights on, it might be too bright for them. 

Benefits of a 10 Gallon Tank for Goldfish

While a 10-gallon tank doesn’t offer the most space for an adult goldfish, it can still be helpful for some goldfish species to thrive. It’s still a good choice if you have already bought a 10-gallon tank because of a tight budget or limited space.

Here are some benefits of keeping goldfish in a 10- gallon tank:

You can Keep Many Young Goldfish

When putting a goldfish in a 10-gallon tank, you need to consider the size of the fish. How big are they? Are they young or an adult? Are you keeping one or two goldfish in that tank?

An adult goldfish grows between 10-12 inches which is too big for a 10-gallon tank. On the other hand, a 10-gallon tank is more than enough when you have juvenile goldfish. 

Goldfish fry are tiny and don’t need a large tank because of they’re size. They also excrete less ammonia, so maintaining the tank won’t be that difficult. According to the general rule for calculating fish tank sizes, you can keep ten juvenile fish of one inch each in this tank.

10 Gallons is Spacious For Small Sized Goldfish Species

With over 200 species of goldfish in the world, you need to know the species of goldfish you’re getting for your 10-gallon tank. You don’t want a goldfish that grows too big for the tank because you’ll need to upgrade the tank sooner rather than later.

Bubble eye and pompom goldfish grow to 4-6 inches. So, they can comfortably survive in a 10-gallon tank.

Other goldfish species like Feeder and Watonai goldfish grow to around 12 inches. So keeping them in this tank won’t give them much swimming room. Especially if you plan to add a heater and a filtration system to maintain proper water parameters for your goldfish. 

Downsides of a 10 Gallon Tank For Goldfish

While a 10-gallon tank Is okay for a single goldfish, it Is on the smaller side. So here are some disadvantages you should know before getting a 10-gallon fish tank for your goldfish: 

Limited Decoration Options

Decorating a fish tank is exciting for most fish keepers because they get to add plants, gravel, and other accessories to keep their fish entertained and healthy. 


Some of these décor options like live plants and caves also help your goldfish’s health and keep them active. 

When a goldfish is an adult, they’ll likely be pretty big for a 10-gallon tank. Any additional decorations you could want to stock in your tank will take swimming space away from your goldfish. 

If you cannot buy a larger tank, ensure you get décor that is easy to maintain and doesn’t take up too much space. With a filter and heater, you might not have room for hiding places like caves. 

Likelihood of Stunted growth

Most aquarists believe that fish grow to their tank size. So a goldfish raised in a fish bowl won’t be the same size as a fish raised in a spacious tank with a proper diet. 

Most fish species have a lifespan of less than a decade, but how long do goldfish live? Unlike many fish, goldfish can live for 10-15 years. These are many years to spend in a small aquarium with no swimming space. By the third year, your goldfish will likely be sick because of toxic build-up in the tank, poor water quality, or boredom.

When they feel cramped, goldfish produce a growth inhibiting hormone that stunts their growth. Although they will still live a healthy life because they are hardy fish, it isn’t recommended. 

If they are goldfish species that grow larger than the average goldfish, they won’t grow to their usual size in a small tank.

Higher Chances of Lower Immunity

The tank living environment highly determines a fish’s immune system because they eat and sleep there. As hardy as they seem, goldfish can easily fall prey to different diseases if their immunity is low. 

Your fish won’t be active or exercise enough to build their immunity in a small tank. Since a 10-gallon tank is harder to maintain, it’s easy for ammonia to build up in the water. And poor water quality is bound to affect your goldfish’s health.

To strengthen their immune system, you must ensure the tank is clean and regularly test the water to maintain proper water parameters. 

Tank Size Calculation Chart

If you want to be more particular about the number of fish to put in various fish tank sizes, you can use a tank size calculation chart. Below are some of the most common fish tank size calculations to help you choose the ideal tank size for your goldfish. 

Per Gallon Calculation

As mentioned above, most fish keepers believe that when choosing the right tank size, you should go for one gallon of water per inch of fish. 

10 gallon fish tank

So if you choose this method, you need to consider the size of the adult fish and not when they are juveniles.

For example, if an adult goldfish grows to 10 inches, the minimum tank size is a 10-gallon fish tank. You can add 5-10 gallons of extra water to provide more swimming space for your goldfish. 

Another standard calculation many aquarists use is 10 gallons per goldfish. This is an easy way to determine how much space the goldfish needs. It is based on the fact that most goldfish grow to 8 inches long. 

Surface Area Calculation

Calculating tank surface area helps fish keepers determine the amount of oxygen the fish needs in their tank. 

You will need at least 24 square inches of surface area for every inch of fish. 

For example, if you get a rectangular fish tank measuring 25 inches long and 10 inches wide, then the surface area of this tank will be (25*10) 250 square inches. 

Two hundred fifty square inches divided by 24 square inches will equal a fish measuring 10.4 inches. This calculation means that this tank can hold a single goldfish that grows to an adult size of around 10 Inches. 

If you want to keep two fish in this tank, they will have to grow to an adult size of 5 inches to be comfortable., or else you’ll have to move the fish into a larger tank. 

Should Goldfish Be Kept in a Fish Bowl? 

While a goldfish can survive in a fish bowl, they won’t be happy with such limited space. It is like living in a tiny box with only enough room to sleep in. You won’t be pleased about that either. 

Goldfish bowls are only suitable if you’re keeping juvenile and small fish before they grow to their full size. An adult goldfish won’t have room to swim or exercise in goldfish bowls. They are very active fish, so denying them the space to move freely is almost cruel. 

Another problem with keeping your goldfish in a fish bowl is that you don’t have space to add the necessary equipment that this species needs. These include a filtration system and heaters to keep the water warm.

Being tropical fish, they need warm water to thrive. If you don’t live in a warm area, you can use water heaters to maintain the proper temperature for goldfish. With such limited space in a fish bowl, all you can add are a few decorations or small aquatic plants. 

Keeping a goldfish in a fish bowl will make your fish unhappy and likely stunt their growth. 


Can I keep two goldfish in a 10-gallon tank? 

If your goldfish are juveniles, they can survive in a 10- gallon tank. As they grow older, they will need more space, so you will have to move them to a minimum tank of 20 gallons. A bigger tank will make these two goldfish comfortable and give you more space to add equipment like heaters and a filter system. 

How big do common goldfish get? 

The common goldfish can usually grow big compared to other species of goldfish. They grow to 8 and 12 inches in size when provided with the proper diet and a comfortable tank environment.  

Goldfish in a 10-Gallon Tank

A minimum tank size of 10- gallons may not be the most spacious for goldfish, but some goldfish species can comfortably live and thrive in this tank. You can keep a school of juvenile or one adult goldfish if they grow to about 5-6 inches in a 10-gallon tank.

With a quality heater system and frequent water changes, a goldfish can grow to be healthy and active. You should also consider the age and species of the goldfish you intend to keep in this 10-gallon tank. 

The proper lighting and water parameters can help your pet goldfish remain strong and happy while living in a 10- gallon tank. But you shouldn’t limit their tank space if you want a healthy fish that lives to a ripe old age.

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