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Why You Should Never Keep Your Goldfish in an Bowl

When people think of beginner fish, they often think of goldfish and betta fish. While both fish are extremely hardy, they are also the most abused fish in the hobby.

For example, betta fish are often kept in tiny bowls of water, less than a gallon, when they actually require a tank of at least five gallons.

Goldfish are also frequently kept in small bowls of water, but this is unfortunately much worse than keeping a betta in a bowl of water.

The average size of the domesticated betta species is only 2-3 inches, so they can still live in a small tank of 5 gallons.

On the other hand, how large do you think goldfish get? 2 inches? 4 inches?

The size of a goldfish is something that nearly every beginner fish keeper gets wrong; in reality, goldfish average between 10 and 12 inches.

The largest goldfish was over 14 inches in length, far too large for any bowl.

The Massive Problem with the Common “Goldfish Bowl” Myth

When you think about the goldfish you saw in bowls growing up, or at a friend’s house, or even at school, they were probably subject to the “classic goldfish care”.

That care essentially consisted of water + fish + bowl, and then they were done!

Of course, the other side of this “care” was replacing the goldfish every 1-3 months after it died.

As you may imagine, this is not the natural lifespan of a fish capable of reaching over a foot in length. With appropriate care, a goldfish’s normal lifespan is between 15 and 20 years, and more than 30 years is possible.

If keeping them in a bowl kills them so quickly, why did that start in the first place?

The exact origins of this disconnect is not known, similar to the origins of keeping bettas in tiny vases and bowls.

The animals die rapidly in these conditions, but those unwilling to put in extra research will simply assume that this is their natural lifespan.

In fact, goldfish care is actually quite complex, and goldfish are not a beginner fish.

They should only be kept by intermediate or experienced fish keepers due to their complex level of care, high level of maintenance, lifespan, and space requirements.

But Don’t Goldfish Grow to Fit the Size of Their Container?

Now, you may be thinking, “Sure, goldfish can get big, but don’t they grow to fit the size of their containers?”.

Well, you’re not necessarily wrong.

Many fish, such as bettas and goldfish, release some variant of a growth inhibiting hormone.

The exact purpose of the hormone is unknown, as the levels in the wild would likely be too diluted to cause any impact.

Goldfish release their own variant of a growth inhibiting hormone, which quickly becomes concentrated inside of a bowl.

This causes them to simply stop growing, resulting in a “stunted fish”. There is unfortunately a great amount of speculation on whether or not this is harmful, and no actual scientific evidence.

While the actual effect of stunting is unknown, it is known that once stunted, a fish will never reach its full size.

There is also a correlation between stunted fish and skeletal deformities, though correlation does not equal causation.

For example, if a fish is already stunted, it is unlikely that the owner is keeping their fish’s diet up to par, and the skeletal deformities may simply be due to malnutrition.

On the other hand, there is no evidence against stunting causing skeletal deformities or other health issues.

It is fully possible that stunting harms a fish in ways that are not visible to us, or even in ways that are, so it is best to avoid this by simply taking proper care of your pet.

The Science Behind Why You Should Never Keep Your Goldfish in a Bowl

If you are a new fish keeper, these words probably sound like a foreign language. But fear not, this is an easy concept to grasp.

If you are an experienced fish keeper and already test your tank regularly, you can skip on to the next section. Although, can a review of the facts do any harm?

One thing that separates fish from most other pets, including cats, dogs, birds, and reptiles, is the fact that they live in water.

Now, I’m sure your first thought about this revelation is “duh” – but there’s more to it than that.

When any other animal produces waste, it doesn’t directly affect them. However, when a fish produces waste, it is broken down by bacteria and becomes part of the water column, which directly impacts the fish, invertebrates, and other tank inhabitants.


When waste is first broken down, it is converted to ammonia. Ammonia is a leading cause of death in fish, as it causes severe chemical burns.

The main issue is that it often causes lethal damage to the gills, suffocating the fish.

Early signs include reddened gills, tattered fins, fish gasping at the surface of the water, lethargy, and fish staying by the outflow of a filter.

Later signs include blackened fins and scales. However, these black marks only appear after the healing process has started, but they show where the fish has been burned.


After a few days to a few weeks, the ammonia is converted into nitrite, which is actually worse.

Nitrite binds to hemoglobin in the blood and prevents it from carrying oxygen, which also suffocates the fish. If the belly of the fish turns red, it is too late to save them.

Luckily, nitrite poisoning can be reversed with a methylene blue bath if caught in time, but this will not heal all the injuries.


Finally, after a few more days to a few more weeks, nitrite turns into nitrate, which is much less harmful.

There is some evidence that it causes immune system damage long term, but aquarium fish seem to tolerate them well.

Any level of ammonia and nitrite, even 0.25 ppm (parts per million) is toxic, or even lethal, to fish.

Nitrate are safe in levels from 20-40ppm, depending on your fish species. It takes about a month to fully cycle a tank, or grow enough bacteria to convert ammonia to nitrate in just a few hours, which keeps your fish from being harmed.

This normally means daily water changes for a month. Or, you can find a different ammonia source and cycle your tank without any fish, though the other ammonia source needs to be added frequently.

Weekly water testing is necessary, as is keeping your filter media clean and safe.

The bacteria primarily live in the tfilter and changing the filter cartridge or washing it in tap water will kill the bacteria. The media should simply be cleaned in a bucket of old tank water.

In order to keep your fish alive and healthy, you will need a water testing kit.

Most any kit will work, but it must be able to test ammonia, nitrite, and nitrate.

Liquid test kits are more accurate than strip test kits, but as long as it can test those three compounds, any kit will do.

How to Ditch the Goldfish Bowl and Set up a Healthy & Sufficient Aquarium

Before we can dive into the type of setup you should be using for your goldfish, it is important to know what type of goldfish you have.

There are two primary categories of goldfish: single tail, or common goldfish, and double tail, or fancy goldfish.

Fancy Goldfish vs Common Goldfish

Before we continue, there are two primary categories of goldfish: single tail, or common goldfish, and double tail, or fancy goldfish.

While both these fish have been selectively bred, the fancy goldfish have been selectively bred for much longer, producing a wider variety of fin, body, and eye types.

The standard rule of thumb is based around the tail. If the fish has one straight single tail, they are a common type of goldfish.

Even if this tail is very long, flowy, and delicate looking, they will fall under the same care category as single tails.

The only exception to this rule is the nymph goldfish, which has one tail, but also has a fancy goldfish type body. Their care is most similar to other fancy goldfish.

A double tailed goldfish generally has a much stockier body and has two tail fins. The body types are so different from the “normal” goldfish that most do not recognize them as a goldfish.

Look up a “Pearlscale” or “Yuan Bao Oranda” and compare them to a common goldfish. Most wouldn’t believe that they are all the same species!

Single Tail Goldfish

There are three main types of goldfish that have only one tail: common, comet, shubunkin.

The common goldfish are the classic orange ones that you see at carnivals or for sale at pet stores for 7-20 cents.

Comet goldfish generally have the same color variations as common goldfish, though there are a few more white and yellow ones, or ones with colored patches.

Their tails are much longer and flowy, similar to a betta’s. However, unlike a betta, their tails do not often hamper their movements.

A shubunkin has a long tail like the comet, but they come in a massive variety of colors.

They were likely primarily bred to appear similar to koi, and they have nearly as many color variants as koi do.

Coupled with the fact that they have a maximum size of 1 foot, instead of the 3-4 foot size of koi, they are a perfect alternative.

Single Tailed Goldfish Care

Any single tailed goldfish, aside from Nymphs, will do much better in a pond than in a fish tank, even a very large one.

They are incredibly hardy and very tolerant of temperatures from freezing to 85 degrees Fahrenheit. Common, comet, and shubunkins are well adapted to outside life and will thrive in a pond.

They need a massive amount of swimming room, with 180 gallons being an estimated minimum requirement for a single goldfish.

All goldfish, both fancies and single tails, produce a massive amount of waste that needs to be diluted.

The larger the goldfish, the more waste they produce, so the massive single tailed goldfish need much more room than the smaller fancy goldfish.

While they can be housed in an aquarium, especially if an unsuspecting person wins one at a carnival, a 55 or 60 gallon should be the bare minimum.

Goldfish need a good mix of open space and hiding areas. If a fish becomes stressed, it must be able to hide, or its immune system will be damaged by the stress.

Having a few moderately sized decorations in the back of the tank, or goldfish safe plants, will have a minimum impact on the swimming area but will provide your fish with some security.

At the very least, they will have some new areas to investigate, as goldfish are very curious and love exploring.

Last, but certainly not least, goldfish need strong filters.

Single tails love water flow, with 8-10 times the tank being an ideal flow rate, though both less and more flow is possible.

For example, if you have a 60-gallon tank, your filter’s capacity should be able to turn over that amount 8-10 times per hour, so it should have a flow rate between 480 and 600 gallons per hour.

Canister filters are ideal for goldfish to achieve this flow, though hang on back, or H.O.B. filters can also be used.

However, canister filters need to be cleaned monthly while H.O.B. filters often need to be cleaned once or twice every week on a goldfish tank.

Goldfish do not need substrate, and it is easier to clean a bare-bottom tank. That being said, they do love to rummage around in substrate, so a sand or tile substrate is not a bad idea.

Gravel substrates can be dangerous for goldfish as they can choke on or swallow the gravel.

Keep in mind that these fish can reach a foot in length, so they will be able to swallow small gravel. However, they will not be able to pass the gravel, and this often results in their death.

As long as they are given enough room and appropriate food (same food as the fancy goldfish) they will live long and happy lives, often nearly 20 years.

Fancy Goldfish

Believe it or not, there are over 20 different variants of fancy goldfish, which is too many to list.

We will list some of the more common ones, which include orandas, ryukins, fantails, ranchus, demekins, bubble eyes, and pearlscales.

All fancy goldfish can be kept in smaller tanks than the common, comet, and shubunkins, but they also move more slowly and have less directional control.

While all these names sound bizarre and overwhelming, each has a unique characteristic that needs to be addressed.

For example, orandas have a wen on their heads, which is a fleshy growth, also called a “hood” or “cap”.

This growth is wobbly and made of soft tissue. While it only grows on the top of an oranda’s head, it may grow down over the eyes and obscure their vision, which requires surgery.

Ryukins have abnormally large humped backs and small-looking heads.

Fantails are characterized by plump bodies and a long double tail.

Ranchus have body shapes similar to an egg and lack a dorsal fin. Their tail fins are normally quite short, and this, coupled with their abnormal body shape, makes it difficult for them to swim.

Demekins normally have shorter, wider bodies like most fancies, as well as medium length tails, but their main difference is with their eyes. The eyes of a demekin are much larger than normal and protrude from their head, which is unique.

Bubble eye goldfish have large, fluid filled membrane sacks the come out from under their eyes. Pearlscales have very thick, often iridescent scales, giving the appearance of pearls.

Their bodies also look like pearls, as the highest quality pearscales are perfectly round spheres and look just like tennis balls.

Each fancy comes with a slight challenge; for one, all those with abnormal body shapes are more prone to developing constipation, swim bladder disorder, and even dropsy.

Any with eye abnormalities cannot be kept with other types of goldfish or fish, and you must be extremely careful in keeping the tank free of anything sharp, including the filter, substrate, and decorations.

Fancy Goldfish Care

The care for fancy goldfish is very similar to that of other goldfish, except they can be kept in aquariums quite easily.

All goldfish should be kept in at least pairs, and a 29-gallon tank is the minimum for two smaller fancy goldfish, such as pearlscales, fantails, or ranchu.

On the other hand, some fancies, such as orandas, reach 10 or more inches in length and need a 40-gallon minimum.

 They should also be provided with hiding areas and swimming room, but you must be very careful about the decorations.

Some, or most, fancy goldfish have tails very similar to those of a betta fish, meaning they are easily damaged. If any part of a decoration seems sharp to you, run a tissue over it. If it tears the tissue, it can tear your fish’s fins.

While goldfish are incredibly interactive, they are not the smartest fish.

It is not uncommon for a fish to curiously check out small openings in decorations, then get themselves stuck in them. This often results in them stripping off their scales, which leaves them open to infection.

Bridge decorations are becoming notorious for this, but only for goldfish. Most fish can either swim through easily or know that they cannot.

Most fancy goldfish are thinner in their fronts than their backs, and they often swim through then get stuck in the middle.

They cannot back out, as their scales prevent that, but they can’t go forwards, and they end up injuring themselves.

Fancy and common goldfish should be fed about the same diet, though fancies need vegetables more often, as they are more prone to constipation.

Sinking pellets are the best for goldfish, as this prevents them from swallowing air with their food.

They should be fed vegetables at least two or three times a week, either raw or cooked. They eat a variety of vegetables, but mine seem to prefer French cut green beans (no salt and no preservatives), blanched kale, blanched spinach, and boiled green peas.

For both goldfish, tank maintenance is similar to any other fish; rinse the filter media in old tank water during a water change and do weekly water changes.

Nitrates in goldfish tanks are normally high, but you need to keep them below 40ppm, which may require water changes twice a week.

So… Are Bowls Still on the Table?

Goldfish require large swimming areas, so we do not recommend keeping your goldfish in any type of bowl.

the exact size being dependent on their breed, but the smallest you can get away with is a 29-gallon tank for the smallest breeds. They need to have a large space, both for swimming and diluting waste.

Goldfish eat frequently, and they eat a lot.

This means that they require more frequent maintenance than other fish, with large 50-70% water changes and filter cleanings being a rather common weekly occurrence.

This is a large investment of time and energy, and if someone is just starting in the hobby, committing to this responsibility for 15-20 years is not a good way to start.

If you happen to find two small goldfish breeds, a 29-gallon bowl, and a filter that will fit onto the bowl’s edge, then you can actually keep a goldfish in a bowl!

However, the average small goldfish bowl will simply kill your fish, and unfortunately, there is simply no way around that.

While goldfish do require a lot of care, they are extremely interactive and rewarding. They are easy to train, and their activity level is intriguing for anyone watching.

Goldfish, or as I like to call them, “water puppies”, are gorgeous and wonderful pets to keep, but they are not for beginners, and they certainly cannot live their full lives in bowls.

Jason Roberts
About Jason Roberts
Jason is an aquarium fanatic that has been a fish hobbyist for almost three decades.

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