Goldfish Tank Size Guide: Which Size Tank For Goldfish Is The Best

Whether you are an experienced goldfish owner or a beginner, you must know how to keep your pet’s life a happy and healthy, despite of the fact that they are hardy creatures. And one of the factors you must consider most is choosing the right size of your goldfish tank. If you are still worry about this issue, you have landed at the right site. In this blog post, we will provide you with everything you should know about goldfish tank size, from the ideal size of tank to methods of keeping your fish tank clear. Scroll down to learn more!

Generally we follow the rule of thumb, which means one goldfish should be kept in at least a 10-gallon tank, and if you plan to have more than one, add 10 gallons more for each. But this is just the minimum tank size for one, there are more factors that you must consider when picking your goldfish tank size.

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How Important Is Tank Size For Goldfish?

The size of the tank has a significant impact on the general health of the goldfish. They require appropriate swimming space as well as proper water flow to maintain an oxygenated atmosphere, remove dangerous wastes, and keep the tank clean.

Planning a fish tank for the long term, including how many goldfish you wish to keep, is critical in creating a healthy atmosphere in the fish keeping world.

Without the proper size goldfish aquarium, you will most likely notice a lethargic, unwell fish that deteriorates in a matter of days to a few weeks.

A lack of swimming room combined with poor filtration can soon lead to a perilous situation for your goldfish and other aquarium fish.

ideal goldfish tank size

Ideal Goldfish Tank Size

To determine the ideal size of a goldfish tank, you’d better first know how big your goldfish will grow. That tiny, lovely goldfish you took home from the pet store has the potential to grow to be 10 to 16 inches long.

Here is a basic breakdown of the size of each full-grown adult goldfish of each type of goldfish for you to determine the best tank size:

Type Of GoldfishGoldfish Length
Type Of GoldfishGoldfish Length
Fancy Goldfish8 inches
Single Tail Goldfish12 to 16 inches
Common Goldfish10 to 12 inches
Comet Goldfish10 to 16 inches
Shubunkin Goldfish10 to 12 inches

A 20-gallon tank is required for one fancy goldfish and a 30-gallon tank for one common goldfish.

But bigger is always better.

Fancies swim in a clumsy manner and do not require a deep tank. Instead, a 20-gallon tank 3 feet long is most suitable for one fish. If you want to add more fancy, add an extra 10 gallons of water for each fish. So we will have  30 gallons for 2 goldfish, 40 gallons for 3 goldfish, and so on.

Comets and common goldfish, on the other hand, should be kept in a 30-gallon tank. These goldfish can grow to be more than 15 inches long. So, if you have two common goldfish, add 12 gallons for each extra fish. This comes to 42 gallons of water for two fish.

Getting a larger tank guarantees that your goldfish have enough swimming space and water volume. These highly energetic fish require plenty of space to move about and grow to their full length.

Consider the space required for other tank mates, decorations, and tank equipment when determining the appropriate goldfish tank size is also needed. These decorations and equipment should not limit the fish’s movement space.

6 Reasons Why You Should Get A Big Tank Size For Goldfish

As we mentioned above, bigger is always better, goldfish bowls and small tanks limit the growth and lifespan of goldfish. We recommend maintaining goldfish in their ideal tank size to avoid this because of the following.

1. Goldfish will have large bodies when they grow up

Goldfish will have large bodies when they grow up

Baby goldfish can range in size from 2 to 4 inches when purchased from a store. These fish can grow to be 12 to 16 inches long over time.

At this length, goldfish require sufficient space to swim and move their large bodies.

2. Goldfish need a spacious room to swim

Did you know that fancy goldfish are less nimble than regular fish? This is due to their long fins, compact body forms, limited vision, and rapid growth of the skull. Fancy goldfish require a larger aquarium so that they can turn smoothly when navigating.

Common goldfish, on the other hand, are clinking swimmers. They charge quite quickly and are extremely enthusiastic. However, their large, hefty bodies limit their ability to turn. Common goldfish, like fancy goldfish, require a larger tank with more swimming space.

3. Larger tanks mean they will have more oxygens

Larger tanks mean they will have more oxygens

The bigger the surface area, the better the aeration of the water. A larger tank with a greater surface area will encourage gaseous exchange. As carbon dioxide evaporates, oxygen enters the water. Believe us, your goldfish will love it so much.

4. Goldfish are social fish

Many people are unaware that goldfish live as sociable shoalers who love the companionship of other goldfish. If you keep two goldfish together, you might notice them swimming together, sitting together, or sleeping together.

Keep a goldfish alongside other goldfish will gain benefits from social interaction and security. And of course when you keep your goldfish with other mates, you must have a large tank to provide them enough space to live together.

5. Goldfish produce a high bioload

Additionally, goldfish need a bigger tank because of their high bioload. These cold-water fish have enormous appetites and are untidy eaters. They generate significant amounts of ammonia, which the fish will find harmful.

A YouTube video on how to lessen ammonia levels in a goldfish aquarium is provided below:

6. They have a long life span

Most goldfish live between 10 and 15 years, although some can live up to 20. A fish shouldn’t stay in a nano tank for this long. Small tanks do not have enough room for decoration or for swimming.

For this reason, keeping your goldfish happy throughout their whole lives requires putting them in a larger tank. The aquarium will provide goldfish extra swimming room, promote interaction, and keep them occupied.

What Goldfish Need In Their Ideal Tank?

Goldfish need a lot of filtration and a roomy swimming area. Your filtration should be somewhat greater than what is advised for the tank size if you have a typical, long-body goldfish such a comet, sarasa, or shubunkin. Keep in mind that goldfish are messy fish that create a lot of waste, therefore more filtration is quite advantageous. However, many fancy types of goldfish do not have strong swimming abilities, thus powerful currents from excessive filtration can easily stress them out. The easiest way to provide appropriate filtration without strong water currents is to baffle or reroute filter discharges to the longest angle of your tank.

Your fish should be able to swim freely and turn around without any problem in a tank that is long enough for them. Artificial ornaments are acceptable so long as they don’t restrict your fish’s ability to swim or turn around. Remember that when your fish develops, any caverns could be rapidly outgrown.

Live plants may be kept with goldfish, but be sure to properly quarantine them. Additionally, if they originate from fish tank systems with other fish, they could introduce germs and parasites. A two-week quarantine in a tank without any fish will stop the life cycles of parasites. Use this opportunity to add some aquarium plant fertilizer to your new plants to help them grow stronger. However, don’t become too attached to your plants because goldfish are notorious plant-eating redecorators.

What’s the most important aspect of my goldfish’s tank?

what goldfish need in their ideal tank

Maintaining water quality is the foremost concern for keeping goldfish, and this cannot be emphasized enough. Only so much of the job can be done for you by your filter! Invest in a reliable water testing kit that enables you to keep track of the variables in your tank, such as ammonia and nitrates, to make sure the water quality is maintained at the highest level. You’ll need to do water changes more regularly to maintain parameters the smaller or more goldfish you have in the aquarium.

To preserve the water quality if you keep your goldfish in a bowl or a small tank, you’ll need to do very regular water changes, sometimes even daily. Everybody does not have the time to perform daily or weekly water changes. You must decide what you can bear in order to provide your goldfish the wholesome environment it needs.

How To Keep The Water In A Goldfish Tank Clean?

We already spoke about how important tank size is, as well as the quality of the water. So let’s look at how to clean the water in your goldfish tank.

Initial goldfish tank cycle

keep water in goldfish tank clean

All fish, even goldfish, should have their tanks cycled on a regular basis. Before putting your goldfish in the tank, you must cycle it, which involves setting it up and letting it run for a few weeks. Three to four weeks of cycling is advised for freshwater species like goldfish. This will ensure that the filter is prepared, that “good” bacteria are present in the water, and that the temperature is exactly perfect.

Select a suitable biological filter

Your choice of filter system for your goldfish tank is crucial. If possible, it should be rated for around 20% more gallons than the quantity of gallons in your tank.

Invest in a Siphon

goldfish tank vacuum cleaner

A siphon functions similar to a fish tank vacuum cleaner. To “vacuum” the fish waste and other trash out of your tank, use it as often as necessary.

Change 25% of the water in the tank each month

Remove 25% of the water from the tank once a month and replace it with fresh water to get rid of the ammonia your goldfish generate.

Put live plants in your aquarium

Live plants in a goldfish tank not only provide beauty but also act as a water filter by eliminating ammonia, carbon dioxide, and nitrates. Additionally, they aerate the water by dispersing oxygen (and do it better than a bubbler). Live plants also decrease algae growth, keeping your goldfish healthier and cutting down on tank cleaning time.

What Happens If The Goldfish Tank Is Too Small?

The goldfish won’t have enough space to swim and explore if the tank is too tiny. Both boredom and health issues may result from this. Goldfish require a lot of room to keep healthy since they are highly active fish.

Goldfish are intended to outgrow smaller aquariums, but if you put them in a little bowl, they can get pretty big. This is due to the growth-inhibiting hormone (GIH), which accumulates when there are frequent or ongoing water changes.

Goldfish are reported to live for 10 to 15 years, although in subpar aquarium conditions, their lifespan may be shortened.

In the ideal environment, goldfish have reached lengths of up to 18 inches (45 cm)! This is far bigger than most people think it is, and it’s all because of the growth hormones they have in their bodies, which enable them to grow to such astounding sizes under ideal living conditions.

However, most goldfish maintained as pets are typically between 4-6 inches or 10-15 cm in length. This nevertheless represents a significant departure from what most people would expect, demonstrating the enormous potential these beings possess.

There are, of course, always exceptions to the norm, and there are records of goldfish reaching heights of up to 2 feet (60 cm). These instances are infrequent, therefore your chances of spotting a fish larger than 1 foot (30 cm) are much higher.

Even so, most goldfish have a maximum size of 6 to 8 inches (15 to 20 cm). This is still the ideal size, so there’s no need to be embarrassed!

What Happens If The Goldfish Tank Is Too Small

Let’s examine the weight of goldfish now that we are aware of their maximum size. The average goldfish weighs between 2.5 and 3 ounces, or 70 and 85 grams. There are always exceptions to the norm, though, and some fish have been found to weigh as much as 6 ounces, or 170 grams.

This is a sizable disparity, but it’s crucial to keep in mind that a goldfish’s weight might fluctuate based on the species and the habitat in which it lives. For instance, goldfish housed in ponds tend to be bigger and heavier than those kept in aquariums.

Most goldfish weigh between 2.5 and 3 ounces, or 70 and 85 grams, on average, however some have been known to grow as large as 6 ounces, or 170 grams.

How Many Goldfish Can I Keep in a Tank?

The greatest response to this issue is for you to utilize your best judgment because there is no simple solution. You’ve succeeded if the environment satisfies all requirements for a healthy goldfish aquarium. Your goldfish are in a suitably sized tank if it has enough room for them to swim, good filtration, and an enriching habitat. Just keep in mind that maintaining the water quality will be more difficult the more goldfish you have in a limited space.

Can different goldfish species live together in the same tank?

“Can you mix various kinds of goldfish together in the same tank?” is one of the most frequent queries from goldfish aficionados. Goldfish come in approximately 200 different varieties. The correct response is that various species of goldfish can be kept together, but they should ideally be around the same size and have a similar swimming inclination. Swimmers who are quick with swimmers who are fast, etc.

It may turn nasty if goldfish with drastically varied sizes and swimming styles battle for food and space. Nobody enjoys seeing their fish battle.

See also: Do Goldfish Need Friends? – Useful Compatibility Information

Videos About Goldfish Tank Size


What size tank do I need for one goldfish?

10 gallons

What size tank do I need for 2 goldfish?

Just follow the rule of thumb, 10 gallons for 1 goldfish, add 10 more gallons for 1 fish more.

Can a goldfish live in a 20 litre tank?

When goldfish are young, they can initially be housed in a compact 20L aquarium. They will soon expand though, so an 80L tank or bigger will need to be purchased within a year.


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