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17.5. Goldfish

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Author : David Bogert

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Time To Read :
13 minutes
Difficulty : Level 6

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Goldfish are a very easy aquarium fish which will thrive even in small aquariums.

Goldfish are the most popular aquarium fish. And they probably have more controversy than any other fish. This is because of a very concerted campaign by PETA (“People for the Ethical Treatment of Animals”) to prevent the keeping of ANY fish in an aquarium, with goldfish being their first target. The whole thing can be boiled down to one bullet point:

It all boils down to an OPINION

It is the OPINION of the PETA folks that goldfish need very large aquariums in order to “thrive”. This OPINION is then parroted by a large group of hobbyists that can best be described as the “Fish Police”. I do not agree with that OPINION. It is my OPINION that goldfish do not need large aquariums in order to “thrive”.

Black Oranda Goldfish
Black Oranda Goldfish

Goldfish Myths

There are a huge number of myths that can be found on social media concerning ALL goldfish.

There have been claims like:

  • The common goldfish commonly grows to a 30 cm SL (“SL” is “Standard Length”, the length of only the body) which equates to 15 inches in length (one commentator said two foot in length!)
  • Goldfish ABSOLUTELY MUST have 30, 40, 80, 100 etc. US gallons of aquarium for the first fish with an extra 20, 30, 40, 50 etc. US gallons for each extra fish.
  • Goldfish are always very dirty fish that ABSOLUTELY MUST have much more filtration and many more water changes than other fish.
  • In a small aquarium the body of the goldfish stops growing . But their organs continue to grow, meaning the fish lives a short pain filled life.
  • The tank needs to have a minimum length of 4, 6, 8 etc. feet to allow swimming room.
  • Goldfish are not a beginner fish.
  • Goldfish are a cold water fish and need cold water to “thrive”.
  • Goldfish are social creatures and need to be in groups of at least three.

These claims are all FALSE

Most of the people parroting these opinions are well meaning folks who just want what’s “best” for the fish. Unfortunately they often come off as being very mean to newcomers to the hobby.

All these claims are simply incorrect opinions unsupported by any research and contradicted by a great deal of simple logic, experience and scientific research. Note that my saying this has resulted in a lot of comments like “This website is a joke” or “ban this idiot”. The “cancel culture” hits the aquarium hobby.

Fancy Goldfish
Fancy Goldfish


If there was one fish which is the king of myths and confusing contradictory advice it would be the goldfish. And yet this is probably the most common fish in the aquarium hobby.

On Facebook aquarium groups and forums, at least once a day, goldfish in a ten gallon tank generate howls of protest from the fish police. And I’m not talking about one or two “They must have a fifty gallon tank” fish police comments, I’m talking at least ten, typically the same people repeating the same worn lines. All “newbies” that go on social media with goldfish in small aquariums should simply block all the fish police who protest. Makes for a much better social media experience.

The simple fact is that the majority of fish tanks sold in the US are ten gallon tanks. And the majority of the fish that go in those tanks are one, two or three common, comet or feeder goldfish. And these fish do just fine the majority of the time. This is simply because that is what these fish have been bred to do over about one thousand years of breeding by Chinese breeders. So if you’ve done that, take heart, you’ll probably be just fine.

Black Moor Goldfish
Black Moor Goldfish

The PETA Goldfish Campaign

There is a concerted effort by PETA (People for the Ethical Treatment of Animals) to “humanize” the fish keeping hobby. They have started this campaign with the goldfish. Their stated goal is to eliminate the keeping of fish altogether. Other stated goals of PETA are to eliminate the use of leather, stop using cows for milk, stop the eating of meat, and stop the “cruel and inhumane” killing of rats in our cities.

If you went up on the PETA website in mid 2019 and looked at the articles section under pets you would have found only four articles on goldfish, with a huge push to populate forums and blogs with “goldfish need ponds” comments. There were no articles on any other pet. So PETA has a heavy duty push on for “humanizing” the keeping of goldfish.

The United Kingdom, Australia and California are hotbeds of PETA and most of the impassioned and overzealous social media comments on goldfish and how to keep them come from the United Kingdom, Australia and California. They have even managed to outlaw the keeping of goldfish in less than a ten gallon aquarium in several areas of the UK.

Comet goldfish
Comet goldfish

These folks are very passionate when it comes to goldfish and being “humane” to them. For instance, take the reaction to the comments of one author, Meredith Clawson. Ms. Clawson has been a goldfish breeder for twenty years and is a recognized expert on goldfish. The excellent quality of her fish speak volumes about how knowledgeable she is about goldfish.

Ms. Clawson wrote an article ( elucidating much the same views about stocking put forth by this article. This article was skewered in social media by the fish police folks. Ms. Clawson said:

“……there are no set “rules” about tank size – there are too many other factors at play from fishkeeper to fishkeeper.


Listen carefully now:

Because water volume does NOT have a direct influence on the health of your goldfish (provided the fish can swim around enough to prevent muscle atrophy).

Water quality does.

Tank size can only play a direct role in the following:

  • How frequently you have to go between water changes
  • How big of a goldfish you can house (i.e. swimming room)
  • And (potentially) aggression between more concentrated tank mates.

If you’re a beginner wanting a good starting point – a general suggestion – and you have the space and money, feel free to start out stocking your fancy goldfish tank at 10-20 gallons per fish.”

Ms. Clawson

Note the stocking level she’s talking about is for fancy goldfish and correlates with what is below in this article. This was a very brave thing for her to write. AND SHE IS A RECOGNIZED EXPERT IN GOLDFISH CARE! Yet as soon as she posted the article there were an avalanche of very passionate and indignant negative comments from the same old fish police.  

Lionhead goldfish
Lionhead goldfish

Some of the comments that flooded in included: “That’s horrible, how would you like to live in a closet your whole life”, “Goldfish need at least 30 gallons for the first fish and 20 gallons for every fish thereafter”, “huge difference between surviving and thriving”, “That aquarium is far too small for those fish”, “That is cruel and inhumane treatment of an animal”, “Goldfish should only be in ponds”, etc. etc.

One fish police said: “that link is completely false information”. An expert who has been breeding very beautiful goldfish for twenty years is providing “completely false information”?

It must be emphasized that these negative comments on social media about the stocking and the tank size of goldfish come from about two dozen very determined individuals. It is the same comments, over and over again, from the same people. Considering there are hundreds of thousands of people on aquarium social media sites, this is a very small, indeed tiny, minority.

These people are obviously very passionate about the “goldfish cause”. But passionate opinion does not equate to scientifically valid facts. BIG DIFFERENCE!

Fancy Goldfish
Fancy Goldfish

Also understand that if one Googles something like “Goldfish Aquarium Stocking” ALL the sites you get will be written by the fish police and ALL the sites will recommend something along the lines of 30 to 50 gallons for the first common goldfish and 20 to 30 gallons for every common after that. And they will recommend at least a 4 to 6 foot tank length. To see one such site (there are many more) just link to

When a true expert comes on to social media and says a goldfish will do well in a ten gallon tank they get vilified by the fish police. So the true experts, not particularly enjoying being vilified, stop making comments on social media. So social media becomes a one sided story.

Fancy goldfish
Fancy goldfish


Millions of goldfish have been kept in relatively small aquariums for many years in the US and elsewhere and done just fine. They lived for many years in these aquariums and were active and healthy. This is exactly what they have been bred to do by over 1,000 years of “inadvertently selective breeding” in China. The Chinese raised their goldfish in small ceramic and earthenware bowls with no filtration and no aeration and the fish that survived were only the ones with very special genes that enabled them to thrive in very small cramped quarters.

On exactly what basis has someone determined that this is “not thriving” and “cruel”? Where is the evidence to that effect? Give me a scientific study which says that.

There is no evidence to suggest that several “narrow bodied” goldfish cannot thrive in a ten gallon as long as there is adequate biofiltration and aeration. And note the nine longest lived goldfish in the world were all in small five to ten gallon aquariums!( )

These two goldfish in the photo below have been in a nine gallon aquarium for 36 and 38 years and certainly appear to be healthy and thriving.

Two 33 year old Goldfish
Two 30+ year old Goldfish

And one must always question the whole concept of “cruelty” to fish and judging whether or not a fish is “happy”. These are human characteristics with little meaning in the fish world. This is the common practice of “anthropomorphism”. Goldfish are NOT humans, nor are they dogs or cats. If goldfish are active, healthy and vigorously swimming then they are “thriving” and not the subject of “cruelty”, in my OPINION. 

Fantail goldfish
Fantail goldfish

Belief Perseverance Effect

Note that we can state with absolute certainty that anyone who believes goldfish are a cold water fish that needs a minimum of 40 gallons of water per fish, etc. etc. and reads this article will absorb absolutely nothing from this article. All the information and data will simply bounce off like pebbles being thrown at a brick wall. They will rationalize and rationalize some more and reject the scientific evidence.

In response to an typical “fish police” comment on social media, a reply was written by one Tumbleweedtumbling. It was excellent and reflects my thoughts much better than anything I could write:

Your response is precisely the kind of hysterical biased personal opinion that my entire article was about. You have no research to quote, no personal experiments and nothing to offer but your opinion. I advise you to go back and read what I wrote very carefully. Obviously you missed everything but your personal beliefs being challenges and you are unable to process that challenge or consider you just might be wrong.

This is something called “belief perseverance effect”. It says that if someone believes fervently in something, even when presented with evidence they are in error, a normal person will rationalize and support their own decision. There is no point in trying to uses logic or science to change such a person’s mind, especially when dealing with a topic like what the humane treatment of a goldfish is.

Internet cartoon

This is just the world we live in and there is no point in trying to fight it. Every time this article is posted in social media someone comes on to say how horrible this article is and that the author is an idiot.



There is one fish often confused with goldfish by beginners. This is the koi. When small it looks much like a goldfish. There are very similar color patterns and they have long finned varieties.  But these fish are pond fish and CAN grow to two feet or more in size. They are not generally a fish I would recommend for the aquarium. But some have had koi in small tanks for three years with no problems. The easy way to tell a koi is that they have long barbs at the corners of their mouth. Goldfish have only very short barbs.

The following tank in San Francisco by Dan Lee generated a huge amount of negative fish police comments like “This is cruel. These fish are only surviving. They are not thriving” LOL. These koi have a huge amount of filtration, the water is crystal clear and they are just fine and “thriving”. I see absolutely no  problem with this koi aquarium. But then that is just MY OPINION! 

Koi in a 300 Gallon Aquarium
Koi in a 300 Gallon Aquarium

Further Articles on Goldfish

For those wanting to delve deeper into keeping goldfish one can go to the following links:

17.5.1. Types of Goldfish

17.5.2. Size of Goldfish

17.5.3. Stocking Goldfish

17.5.4. Goldfish Care

Aquarium Guidelines for a Beginner

Note that many newcomers start out with goldfish. So if one is a newcomer to the hobby of freshwater aquariums we recommend reading these general articles on the first aquarium:

1, What do you do when you buy your first aquarium? This might help you:

1.1.1. What to do with Your First Aquarium

2, Because fish pee a chemical called “ammonia” and that ammonia is bad for a fish, it is desirable to treat a new tank for four to six week with a process called “cycling”:

1.1.2. A Simple Way to Cycle an Aquarium

3, All fish food found on the shelf of the local fish store is fine for all fish:

1.1.3. Fish Food Simplified

4, Other than removing chlorine the water parameters are not important:

1.1.4. Water Parameters

5, Filter are needed for all fish. But it is important to not replace or clean the filter too often:

1.1.5. Filters for the Newbie

6, The media in the filter is also important:

1.1.6. Filter Media

7, Good aeration give healthy fish:

1.1.7. Aeration

8, Starting a new tank one should always have a light stocking of just a few fish, with neons, discus, and a few other fish being avoided:

1.1.8. Stocking a Tank

9, A brown film will develop on pretty much all surfaces in any new tank. Experienced hobbyist just live with it. It is part of a healthy aquarium:

1.1.9 Brown Algae in a New Tank

10, One of the most challenging tanks to keep is a tank with five or so three inch fish and five live plants. Any beginner should start with plastic plants:

1.1.10. Plants and the New Hobbyist

11, New fish get one disease quite often. This is white specks on the skin of the fish which is called “white spots” or “ich”:

1.1.11. The Most Common Fish Disease – Ich

12, And if you want good, healthy, “happy” fish, there are five critical elements to doing that:

1.1.12. How to Make Fish Thrive