Do Goldfish Need a Big Fish Tank? (Answered)

If you are wondering, do goldfish need a big fish tank then you are in the right place. 

In this article, I’m going to answer the same question.

Goldfish are very messy fish and they can grow very large that’s why they need a big fish tank. A single goldfish need at least a 20 gallon tank and you’ll need 10 gallons for each additional goldfish.

Now you know that goldfish need a big tank. But how big of a tank you’ll need to keep your goldfish depends on the type of goldfish you want to keep in your tanka and the number of goldfish you want to keep in the tank. And this is what I’m going to cover in this article now.

Keep reading…

Do Goldfish Need a Big Fish Tank? (Answered) image

Why do goldfish need a big fish tank?

Goldfish image with text "Why do goldfish need a big fish tank?"

There are a couple of reasons why goldfish need a big tank.

1. Goldfish produces a lot of waste

Goldfish are considered very messy fish i.e. they produce a lot of waste in the fish tank. 

The reason goldfish produce a lot of waste is that goldfish don’t have stomachs as other animals and humans do!

When goldfish consume food, as the food moves through the intestine of the goldfish, it breaks down and the nutrients from the food are absorbed in their body.

Fun fact: Goldfish have an intestine twice the length of their body.

Because goldfish do not have stomachs as other animals do, they cannot store food in their bodies for a long time.

The food moves through their digestive system relatively fast and gets excreted out fast. And this is the reason goldfish produce a lot of waste in the fish tank compared to other fish.

As goldfish produces a lot of waste in the tank the waste produced by the goldfish breaks down in the tank and gets converted into ammonia then nitrite and then finally into nitrates (if your fish tank is cycled).

Now nitrate is not as harmful to the goldfish as ammonia is but if the fish tank contains a lot of nitrates (more than 40 ppm) then it is fatal for the fish.

Now as goldfish produce a lot of waste in the tank the nitrates can build up pretty quickly in the tank which is, as I said earlier, deadly for the fish.

And this is the reason you’ll need a big goldfish tank because in a large tank you’ll have more water so the nitrate will build up slowly or in other words the nitrates will be diluted due to more water in a big tank.

Now when the nitrates reach more than the 40 ppm mark then you’ll need to remove the nitrate. 

There are two ways to remove nitrate from the tank.

  1. Partial water change
  2. Plant a lot of plants in the tank.

Generally, you’ll need to do a water change to remove the nitrate because planting a lot of plants in a goldfish tank is not a viable option because first, goldfish are known to eat up the live plants you planted in the tank so most plants will not survive in the tank.

And second, you’ll need a lot of plants to get rid of all the nitrates from the tank.

Another benefit of having a big goldfish tank is that you’ll need to do water changes less frequently compared to if you have a smaller tank.

2. Goldfish can get pretty big

The second reason goldfish need a big tank is that goldfish can get pretty big. 

According to Guinness World Records, the world’s longest goldfish was owned by Joris Gijsbers and measured 18.7 inches (source)

Generally, goldfish can get around 14 inches in a fish tank. For goldfish to comfortably live in a fish and to have sufficient space in the tank to swim around you’ll need a big fish tank for goldfish.

What happens if you keep goldfish in a small tank?

Goldfish image with text "What happens if you keep goldfish in a small tank?"

If you keep goldfish in a fish tank then you’ll need to do the water changes very frequently. 

Also, as goldfish can grow pretty large (generally around 14 inches) the goldfish will not have sufficient room to swim around in the tank.

This can affect the proper growth and development of the fish. And it can reduce the life expectancy of the fish.

How to choose the right fish tank size for your goldfish?

Goldfish image with text "How to choose the right fish tank size for your goldfish?"

When it comes to tank size for your goldfish two things come into play

  1. The type of goldfish you want to keep 
  2. The number of goldfish you want to keep in the tank

1. Goldfish tank size according to the type of goldfish you want  to keep in the tank

Different types of goldfish grow to different sizes. That’s why you’ll need to house them according to their size.

Common goldfish and Comet goldfish 

Common and comet goldfish grow larger than fancy goldfish that’s why they need a larger tank compared to fancy goldfish.

For a common goldfish and/or Comet goldfish, you’ll need at least a 30 gallon tank. 

What if I want to keep two Common goldfish or Comet  goldfish in the tank

If you want to keep two Common goldfish or Comet goldfish then you’ll need to keep them in a 40 gallon tank.

When it comes to deciding on the tank size if you’re keeping more than one Common goldfish or Comet goldfish is – 30 gallons for the first goldfish and then 12 gallons for every other goldfish.

For example, if you want to keep three Common goldfish in a tank then you’ll need 30 gallons for the first goldfish and then 12 gallons each for the remaining two goldfish.

So in total, you’ll need 54 gallon tank for the three Common goldfish.

Generally speaking, keeping more than three Common goldfish or Comet goldfish in a  fish tank is not practical. That’s why generally, you’ll see more than three Common or Comet goldfish in a fish pond.

Fancy goldfish

Generally, Fancy goldfish do not grow as large as Common goldfish or Comet goldfish that’s why you’ll need a relatively smaller tank for keeping Fancy goldfish.

If you want to keep a Fancy goldfish in a tank then you’ll need at least a 20 gallon tank. 

What if I want to keep two fancy goldfish in a tank?

If you want to keep two Fancy goldfish in the tank then you’ll need 30 gallon tank. 

When it comes to deciding on the tank size for your Fancy goldfish tank if you want to keep more than one Fancy goldfish, here’s a simple rule you should follow- 20 gallons for the first Fancy goldfish and then 10 gallons extra for each Fancy goldfish.

For example, let’s say you want to keep three Fancy goldfish in your tank then as per the rule, you’ll need 20 gallons for the first Fancy goldfish. And then extra 10 gallons each for the two Fancy goldfish.

So in total, you’ll need a 40 gallon tank if you want to keep three Fancy goldfish in your tank.

Do goldfish prefer long or tall tanks?

Goldfish image with text "Do goldfish prefer long or tall tanks?"

You should choose a long tank than a tall tank for goldfish. This is because if you keep goldfish in a taller tank then because of their fin shape or body shape, especially because of the body shape of Fancy goldfish like Pearlscale goldfish, Tosakin goldfish they lose their buoyancy balance due to the pressure in a tall tank.

Keeping goldfish in a long tank will also provide them a lot of space to swim around in the tank.

Tank SizeL x W x HEmpty WeightFilled Weight
20 gallon Long30″ x 12″ x 12″25 lbs225 lbs
29 gallon30″ x 12″ x 18″40 lbs330 lb
30 gallon Breeder36″ x 18″ x 12″48 lbs348 lbs
40 gallon Long48″ x 12″ x 16″55 lbs455 lbs
50 gallon36″ x 18″ x 19″100 lbs600 lbs
75 gallon48″ x 18″ x 21″140 lbs850 lbs
125 gallon72″ x 18″ x 21″206 lbs1206 lbs

FAQs

Goldfish image with text "faq"

Can 1 goldfish live in a 1 gallon tank?

A goldfish cannot live in a 1 gallon tank. You’ll need at least a 20 to 30 gallon tank to keep a single goldfish.

Can goldfish live in small tanks?

Goldfish can not live in a small tank because they can grow very big and they are also very messy fish so you should keep them in a larger tank to dilute the waste produced by the goldfish.

Can goldfish live in a bowl?

Goldfish can not live in a bowl. This is because goldfish can grow pretty large and bowls are generally very small for goldfish. 

Is a 20 gallon tank big enough for a goldfish?

You can keep a fancy goldfish in a 20 gallon fish tank. But if you want to keep a comet goldfish or common goldfish then you’ll need at least a 30 gallon tank for a single goldfish.

How many goldfish can I put in a 30 gallon tank?

You can put a common goldfish or comet goldfish in a 30 gallon tank. And you can keep two Fancy goldfish in a 30 gallon tank.

Conclusion

Goldfish can grow pretty large and they are very messy fish that’s why you should keep them in a big tank.

If you want to keep a single common goldfish or comet goldfish then you’ll need to keep them in at least a 30 gallon tank. And then 12 gallons more for each additional fish.

If you want to keep a fancy goldfish then you’ll need to keep them in at least a 20 gallon tank. And you’ll need 10 gallons extra for every additional fancy goldfish.

Goldfish related articles:

Sources:

Standard fish tank sizes

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