Best Tank Size For Goldfish (Tank Size Tips and Tricks)

20 gallons tank size

Goldfish are often kept in aquariums, but they can get very big. The best tank size for goldfish depends on the species and number of goldfish you intend to keep. As a general rule, choose an aquarium at least 20 gallons for one goldfish and 40 gallons for two goldfish. You will need a larger tank to maintain more than two goldfish.

In this guide, you will read all you need to know about tank size and the tips and tricks in choosing that perfect tank for your goldfish to live a happy and comfortable life.

You may also see how to care for goldfish: step-by-step goldfish care instructions here

Let’s get started!

The size of the tank is an essential part in the overall health of your goldfish and their level of contentment.

A small tank can result in several issues, including stunted growth, decreased water quality, and elevated stress levels. Because goldfish create such a large amount of waste, even a relatively small tank can soon become filthy, which can have a negative impact on the fish’s health and lifespan.

On the other hand, if the tank is large enough, your goldfish can swim freely, exercise, and explore their surroundings.

In addition, it offers a sufficient volume of water, which helps dilute waste and preserve the purity of the water.

The larger the tank, the more stable the environment will be, and the less likely it will be that there will be rapid shifts in temperature or pH levels.

Best Tank Size for Goldfish

20 gallons tank
20 gallons tank

The type and size of the goldfish will determine the best tank size for those fish.

Let is discus further how the types and sizes of goldfish can help in determining the most suitable tank size for the number and variety of goldfish that you plan to keep:

Single Fancy Goldfish

It is recommended that you use a tank that has a size of at least 20 gallons if you intend to keep a single fancy goldfish.

Compared to their peers with slimmer bodies, fancy goldfish have more delicate fins that flow smoothly and move slower.

By giving them plenty of room, you ensure they can swim without worrying about getting their fins twisted up.

Single Common or Comet Goldfish

One of these goldfish will need a tank with a minimum capacity of thirty gallons to thrive.

A larger tank is required for a single goldfish, whether a common or comet kind.

These types of goldfish are more active than fancy goldfish and have the potential to grow to greater sizes.

Multiple Goldfish

It is essential to examine the space requirements of many goldfish and their potential for growth when you have made up your mind to keep more than one goldfish in an aquarium.

As a general guideline, you should provide at least 10 gallons (37 liters) of water for every goldfish you keep.

For instance, if you want to maintain three fancy goldfish properly, you should have a tank of at least 30 gallons.

Goldfish are sociable creatures who do best around others of their species. However, stocking a tank with excessive goldfish might cause it to become overcrowded and degrade the water quality.

Be aware of the tank’s capacity and check to see that the goldfish have sufficient space to swim and interact with one another without feeling cramped.

Factors to Consider When Choosing the Best Tank Size for Goldfish

A. Types of Goldfish and Size

The requirements for the tank size will vary depending on the size of the goldfish and the species of goldfish you have.

The single-tailed and the fancy types of goldfish are the two most common types.

Goldfish with a single dorsal fin, like the Common and Comet types, can grow rather large and hence require more room to swim. Because of their shorter bodies and broader fins, fancy goldfish, such as the Fantail and the Oranda, are not very agile swimmers as common goldfish.

B. The Potential for Growth and the Size at Adulthood

Goldfish can experience substantial growth throughout their lives. When selecting a tank, consider the fish’s eventual size.

Fancy goldfish typically reach a length of between 6 and 8 inches (15 to 20 cm), although single-tailed goldfish can grow to lengths of up to 10 to 12 inches (25 to 30 cm) or even longer.

When you give them enough room to grow, you can avoid problems with their development and the accompanying health problems.

C. The Quantity of Goldfish

The number of goldfish that you intend to keep should also be something that you give some thought to.

Goldfish are very social fish that do best when kept in groups. However, the bioload will increase with each new goldfish put into the tank, so additional filtration and room will be needed to preserve the water quality.

Too many goldfish in the tank can increase the risk of stress, illness, and stunted growth.

D. Filtration and Water Quality Requirements

Goldfish have a well-deserved reputation for producing a considerable lot of waste.

It is necessary to have adequate filtration to keep the water quality at a high level and prevent the buildup of ammonia and nitrite, which can harm the fish.

A larger tank has a greater volume of water, which in turn dilutes the waste and lessens the effect it has on the fish.

E. Tank Shape and Swimming Space

Also, take into consideration the shape of the tank. Tanks with a wider base are preferable for housing goldfish as opposed to tall and small ones.

This affords them a sufficient amount of swimming space, as well as maximizes the oxygen exchange at the water’s surface.

Additional tips and tricks for selection best tank size for goldfish

A. Single-tailed Goldfish

Minimum tank size: A single-tailed goldfish, such as the common goldfish, should have a tank of at least 20 gallons (75 liters).

This is the minimum tank size recommended to provide sufficient area for their needs in terms of growing and swimming.

Ideal tank size: For a single-tailed goldfish, the ideal tank size is 55 gallons (208 liters) or more, and this should be your goal to provide the fish with the very best living conditions available.

The more space they have, the better for their health and the happier they will be.

B. Fancy Goldfish

Minimum tank size:  It is advised that the tank be a minimum of 20 gallons (75 liters) in capacity to appropriately fulfill their needs due to the more delicate nature of their fins.

Ideal tank size: A tank that is at least 40 gallons (151 liters) is recommended for keeping fancy goldfish because this size provides the best environment for their health.

The additional room makes for a more comfortable environment while lowering the chance of fin damage.

40 gallons tank size
40 gallons tank size

Tips for Setting up the Goldfish Tank

If you follow these tips, you may provide your goldfish with an environment that is optimal for their growth:

A. Choosing the right tank:  Consider the suggested tank sizes for your particular species of goldfish, and choose a tank with dimensions that are suitable for their needs.

B. Setting up appropriate filtration: Put in place a filtration system capable of managing the bioload caused by your goldfish while preserving the high quality of the water in the tank.

C. Selecting Appropriate Decorations: Select risk-free decorations for goldfish, avoiding those with pointed edges or small gaps that may cause them to become trapped.

D. Keeping proper water parameters: It is important to perform routine tests of the water parameters (ammonia, nitrite, nitrate, and pH) and to change the water as needed to ensure that the conditions remain optimal.

E. Monitoring the behavior and health of fish: Ensure that you keep a close eye on your goldfish at all times, checking for any symptoms of illness, unusual behaviors, or signs of stress. If assistance is required, look for it from a professional.


Regarding the health and well-being of your goldfish, picking the best tank size for your goldfish is of the utmost importance.

You may create an environment that is conducive to the growth of goldfish by taking into account aspects such as the species of goldfish, their potential for growth, their filtration requirements, and the design of the tank.

Keep in mind that a larger tank provides various benefits, including an improvement in the quality of the water, a reduction in the amount of stress experienced, and enhanced growth. Therefore, provide your goldfish with the room they require, and enjoy seeing them thrive.

We hope you find this post interesting; kindly subscribe to the “Pets and Homestead” newsletter.

Related post: What Fish Can Live with Goldfish (The 35 Best Goldfish Tank Mates & Companions)