How Many Goldfish Per Gallon? (Based on Fish Types & Growth)

how many goldfish per gallon

Just how many goldfish per gallon is ideal? It’s often recommended to have a 1-inch goldfish per gallon of water. However, it all boils down to tank size and the type of goldfish. You need to consider swimming space and how big a specific type of goldfish can grow.

You can house one small goldfish per gallon, but you can’t have one baby yet large-growing tropical fish per gallon. Some fish, like Arowanas, can grow from 2 inches to 3 ft.

Based on the Fish Types and Growth

1. Common Goldfish (20 gallons for each)


Common goldfish are known for their vibrant color, elongated body, and short tail. They are popular among newbie fishkeepers because of their appearance and easygoing nature.

Although they can grow up to 12 inches in length when kept in a large space like a pond, most common goldfish are only 4-10 inches big. They need natural plants and decorations to explore.

2. Comet Goldfish (30 gallons for each)


Identical to common goldfish, comets are distinguished for their long tails. They are usually coated in yellow, white, or blotchy orange colors.

Comet goldfish are super laid-back, but they enjoy being active! They can grow anywhere between 4 and 12 inches as well, so it’s not a good idea to house them in a very small tank.

3. Shubunkin Goldfish (75 gallons for each)


Shubunkin goldfish are comparable to comets, except for their calico appearance. Bred for their coloring, they normally come with orange, blue, white or black spots.

Shubunkins are omnivorous goldfish that can get up to 9 or 18 inches long. They require around 75 gallons of water to thrive.

4. Wakin Goldfish (30 gallons or more for each)


This goldfish is an active swimmer, which makes it a pond pet favorite. The fancier goldfish varieties many are familiar with now are said to have their roots in this species. Because of its body shape, though, most simply classify it as common.

With an average length of 10-12 inches, Wakin goldfish live in a 60-78 ºF environment and have a 12-year life expectancy. You must keep them in a 30-gallon (or bigger) tank.

5. Fantail Goldfish (30 gallons or more for each)


The epitome of “fancy”, fantail goldfish possess gorgeous flowy tails. It’s advised to keep at least two goldfish in an aquarium to encourage interaction and companionship. 30 gallons or more is required for each fantail as they grow 6 to 8 inches long.

Fantails are omnivorous. Feed them high-quality food that replicates their natural diet and is packed with all the essential nutrients.

6. Ryukin Goldfish (30 gallons or more for each)


Ryukin goldfish are the eastern version of fantails. They are tall 6 to 8-inch goldfish with a noticeable shoulder hump behind the head.

You need to house ryukins in a 20 or 30-gallon nano tank. Also, don’t keep them with weaker fish breeds because they tend to be semi-aggressive.

7. Pearlscale Goldfish (30 gallons for each)


A bit weird-looking, pearlscale goldfish have a round body covered in thick scales. They are more sensitive than other goldfish breeds, so they are not the best option if you’re inexperienced.

Pearlscale goldfish are ideal for 20 to 30-gallon tanks–they can grow up to 8 inches long. Their meek personality makes them awesome companions for other calm creatures with the same habitat preferences.

8. Bubble Eye Goldfish (10-30 gallons for each)


Unique for their eyes, this goldfish has sacks that grow with their height! You need to take extra care of them by removing any sharp objects in your aquarium.

Often 3-4 inches in length, you may keep bubble eye goldfish in 10, 20, or 30 gallon tank. They are very chill, so they can definitely live with other non-aggressive fish, especially other goldfish.

9. Telescope Eye Goldfish (20-30 gallons for each)


The telescope eye goldfish is among the most popular types of fancy goldfish. This type is characterized by its rounded, protruding eyes (as its name implies).

Telescope eye goldfish, which are typically 4–8 inches long, need a tank that is at least 20 gallons or more. These fish are omnivorous and particularly enjoy eating frozen or live shrimp, different flakes, and bloodworms.

10. Oranda Goldfish (30 gallons or more for each)


Oranda goldfish are around 8 to 12 inches long, which makes them thrive in no less than 30 gallons of water. They are cute, passive fish who like checking out plants and spending their time gently swimming around.

To avoid infection, keep in mind that their head needs protection. Keep them comfortable as well by maintaining a 65–72°F environment.

11. Lionhead Goldfish (20 gallons for each)


Similar to common goldfish, the lionhead goldfish is a calm freshwater fish. They were bred to resemble Chinese guardian lions and are mainly red and orange in color.

Lionheads’ size ranges from 5 to 8 inches. They are omnivores who feed well on plant matter and meaty flakes or pellets.

12. Black Moor Goldfish (20 gallons for each)


The black moor goldfish is one of the most well-liked species of goldfish. They are known for their telescopic eyes and black scales. The more black their scales are, the higher their perceived quality is.

This goldfish is peaceful and easy to care for. Their average length is 6-8 inches.

How Many Goldfish Should Be Kept Together in a Tank?


Before you put your goldfish in a tank, you must learn the best size for them. How many gallons do goldfish need? Let’s take a look.

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  • 10 Gallon Tank – An ideal tank size for 1 goldfish is 10 gallons. Common goldfish are great for this size.
  • 20 Gallon Tank – you can keep 1 or 2 goldfish in a 20 gallon tank, as long as they don’t grow way more than a few inches.
  • 30 Gallon Tank – you can typically keep 3–4 goldfish in a tank of 30-35 gallons. Again, this varies according to fish size and water filtering system.
  • 50 Gallon Tank – keeping in mind the factors that affect the right number of gallons for a goldfish, most 50-gallon tanks can house 3-5 medium-sized goldfish.
  • 160 Gallon Tank – 120 to 160-gallon tanks are ideal for 6-8 goldfish. Maintenance is more than necessary because more fish means more waste.


As a general rule of thumb, the number of gallons per goldfish will always depend on fish size and breed, filtration, tank decorations, and surface area (where gas exchange takes place).

Number of goldfish per gallon for a pond

Taking into account the setup, filtration, plus the amount of goldfish and their breed, a minimum depth of 3 feet is necessary to prevent freezing, and the water body must have a big surface area to improve gaseous exchange inside.

A pond’s capacity affects its water quality, so the volume of water is just as crucial as space. A small amount of water will lead to quick nitrogenous waste contamination.

Importance of choosing the right size for a goldfish tank

If you want your goldfish to grow well and live a long, healthy and happy life, you must choose the right tank size. Like any fish, they need enough space to freely swim and have fun as much as they want.

Factors that affect goldfish population

Competition for food and minerals, the number of water pollutants, the environment, weather, and other factors may be limiting elements that have an impact on goldfish population.

Fish will stop spawning due to increased competition for food and nutrients, while an increase in  population means they will likely produce more waste. The water will be polluted and will kill all the fish.

Frequently Asked Questions


What are the ideal tank mates for goldfish?

Some of the best companions for goldfish are zebra danios, cherry shrimp, platy, white cloud mountain minnows, and rosy barbs. Snails like mystery snails and Japanese trapdoor snails as well as other goldfish are great too.

Which fish should you not keep with your goldfish?

Bettas, mollies, cichlids, tetras, and common plecos won’t make nice tank mates for your goldfish. They can be aggressive or easily stressed to be with.

What is the best tank size for two goldfish?

A 20-gallon tank will provide the comfort and space two average goldfish need. However they can benefit even more from bigger tanks.


So, how many goldfish per gallon can you keep? Although it’s often advised to keep one inch of goldfish per gallon of water, you must make your calculations while taking into account the space, filtration, tank ornaments, and surface area and goldfish breed and size. Once you’ve got all that down, you’ll know how many fish you need.

A 20-gallon tank is ideal for one or two medium-sized goldfish, while a 160-gallon is best for 6 to 8 goldfish. More water means less maintenance (less waste accumulation). If you’re a newbie, single-tail fish or fantails are great for you.