Goldfish Myths: know the facts!

Goldfish are one of the top pet choices in the world!

red cap oranda goldfish


The answer is simply because they are fascinating creatures!

As popular as goldfish are as pets, it’s incredible how little their owners know about them.

In fact, many people choose to believe the myths circulating the topic rather than research and educate themselves on their finned friend.

It is essential to know the difference between fact and myth in order to properly care for and own goldfish.

This article will discuss various myths as well as the underlying truth of the matter.

Myth #1: Goldfish are strictly plant-eaters

This is a myth because goldfish are actually omnivores. Omnivores are creatures that live on a diet of both plants and animals.

Yes, goldfish eat meat!

goldfish diet

This myth was likely created because goldfish are often seen nibbling on their live aquatic plants or, in conjunction with the myth that goldfish do not have teeth and therefore cannot eat meat.

Well, it is very true that goldfish enjoy nibbling on their aquatic plants.

They are munchers which mean that they love to snack between feedings and their aquatic plants and algae are excellent sources.

 However, it is entirely false that goldfish do not have teeth.

They do!

They are located near the back of their throat. These teeth are called pharyngeal teeth.

They cannot be easily seen by the owners, and therefore, many owners assume they are not there. 

Goldfish use these teeth to chew the various types of food in their diets. These foods include:

Myth #2: Goldfish must live in cold water

This myth is not entirely false. Goldfish can technically survive in cooler temperatures.

However, they can also technically survive in warmer temperatures. The difference being that cooler water contains more oxygen than warmer water.

fancy goldfish

Therefore, the warmer water would run out of quality oxygen at a faster rate than cold water.

Aquariums with goldfish and warm water may need to undergo a water change more often than an aquarium with goldfish and cold water.

The other explanation of this myth is that goldfish should not live in cold water because they are far less mobile in cold water than they are in warmer water.

Slow swimming fish will likely have a harder time reaching the surface for food and will not be nearly as active.

 Aquariums that are too warm may also speed up the bacteria and algae growth rate which can cause harm to the goldfish.

Therefore, the bottom line in that room temperature (60ºF to 70ºF) is generally a comfortable temperature for goldfish to live in.

Room Temperature
Room Temperature

Myth #3: Goldfish do not have long lifespans

This myth was likely developed based on how quickly goldfish tend to die while in our care.

However, the information is entirely false!

Goldfish that are kept as pets are not dying as a result of their short lifespans; they are dying because of their improper care provided by their owners.

 It is more accurate to say that goldfish are capable of living for nearly 50 years, but, they are a delicate fish that requires certain conditions to make it that long.

how long do goldfish live

Regular water changes, tank cleanings, proper diet, filtration systems, water temperature, and even overpopulating a tank can all be the difference between life and death of a goldfish.

Goldfish have the potential to be a life-long commitment for you and your family if you are prepared to put in the extensive time and effort (and money) to keep them happy and healthy for the greater majority of your life.

Myth #4: Goldfish should live in fish bowls

This myth is an example of how goldfish owners are significantly reducing the lifespan of their fish.

Goldfish may be capable of surviving a variety of conditions. But, they simply will not live a long, happy and healthy life living in a fish bowl.

Goldfish require a rectangular aquarium that is at least 30-gallons (add 20-gallons for each additional goldfish inhabiting the tank).

clean a fish tank

Goldfish are a very messy type of fish. They expel quite a bit of waste throughout the course of the day which causes their water quality to decrease gradually.

If the goldfish lives in a bowl, then he will contaminate his water much faster than he would in a large tank.

Also, fish bowls do not have filtration systems to purify the water of bacteria, chemicals, and various other contaminants.

They also lack aeration, space to grow, and proper water volume. Goldfish (even one living alone) needs adequate space to swim, sleep, eat, breathe, and grow.

The fish will not be able to do any of those things well in a fish bowl.

Myth #5 Goldfish are feeder fish

Goldfish are complicated, high-maintenance and beautiful creatures that make excellent pets.

However, they are also easy to reproduce, easy to find and are quite abundant.

school of goldfish

Therefore, many people believe that goldfish are feeder fish (fish that are bred to be fed to larger animals and fish).

While there is some fact to this (i.e. their abundance etc.), there is also quite a bit of misinformation.

Goldfish are not a proper nutritional meal for an animal or larger fish.

They are incredibly high in fat, and they are full of thiaminase. Thiaminase will destroy thiamin (Vitamin B1) thus causing the animal or large fish to have a Vitamin B1 deficiency.

A Vitamin B1 deficiency will likely lead to severe illness and even death.

vitamin b

Therefore, goldfish are not a decent feeder fish option. If you are looking for a feeder fish option, you may want to consider home-bred tropical fish.

For more specific options consult an expert in this field.

Myth #6: Goldfish are the same species as Koi fish

No, Koi fish and goldfish are not the same species of fish. However, they are both members of the same family known as Cyprinidae.

The Cyprinidae family is also sometimes referred to as the carp family or even the minnow family.

There are roughly 2,400 different fish species in North America, Asia, Africa and Europe that belong to this large fish family.

Koi fish are known as Cyprinus Carpio, and goldfish are known as Carassius Auratus.

school of koi fish

However, both fish species are capable of hybridization and contain various similarities.

Myth #7: Goldfish do not grow larger than their tanks

This is yet another “myth” that unfortunately holds a bit of truth. T

he truth is that goldfish do not have a “growth limit.” They will continue to grow until they die.

The unfortunate part to this is that more often than not, goldfish die due to improper care, neglect, poor living conditions, and various other issues.

The size of their tank plays a role in this as a smaller tank (or bowl) will not meet all of their needs, thus causing them not to grow to their full potential and die because of lack of proper care.

The best way to avoid this is to devote time, effort, and money to your goldfish and the tank.

Even if you only plan to have a single goldfish in a single aquarium, you will still have quite the responsibility on your hands.

how many goldfish can i fit

For a single goldfish (approximately 2 inches to 3 inches in size) choose a 30-gallon aquarium (minimum).

 As you notice your goldfish growing, purchase a larger tank. Continue to increase the size of the tank as your goldfish increases in size.

Alternatively, owners can cut to the chase and choose a large rectangular aquarium from the beginning and watch him grow into it!

Myth #8: Goldfish do not have a memory longer than 3-seconds

This myth is entirely false and is thought to originate in conjunction with the fish bowl myth.

It was once believed that goldfish should be kept in a fish bowl because their memory only lasted about three seconds long and therefore they could never experience boredom.

However, this is far from the truth! In fact, goldfish are capable of remembering their owners, events, etc. for about three months!

After three months, events or people that only came around a few times may be forgotten.

ranchu fancy goldfish

However, owners and other constant variables in the goldfish’s life may not be so quickly forgotten as long as they remain the same.

Goldfish are also capable of telling time, learning tricks, and even getting used to a scheduled routine.

Myth #9: Each Goldfish type is its own species

This myth may not be one that you hear very often, but it one that should be debunked anyways.

There is a vast variety of goldfish, many of which can be found at your local pet store or aquarium. Nonetheless, each goldfish type belongs to the same species of fish.

This is very similar to the way that there are many kinds of dogs and cats in the world but, that they are all members of the canine family or the feline family.

The reason behind this myth is likely due to the variety of physical appearances between types of goldfish.

For example, the fantail goldfish, the Lionhead goldfish, the comet goldfish, the common goldfish, the bubble eyed goldfish, and the Oranda goldfish are all members of the goldfish family, yet they share very little (if anything) in physical appearance.

types of fancy goldfish

This likely led people to believe that each goldfish type was actually its own separate species.

Also, very few goldfish actually resemble their ancestral counterparts, the wild carp.

In general, the only type of goldfish that appears anything like the wild carp is the common goldfish.

They are incredibly similar in physical appearance with the exception of their size (carp tend to be larger) and their color (wild carp are more silver in color and goldfish range in bright colors and patterns).


Myth #10: Goldfish excrete a toxin that is hazardous to other fish

This is a myth because goldfish are not “toxic” in any way.

However, they do excrete ammonia which can be dangerous if not controlled with proper filtration systems, water changes, and tank cleanings. 

It should be noted that this goes for all fish!

goldfish care 101

Goldfish are thought of as a messy, hardy fish species which means that they eat a large amount of food, digest it rapidly, and then excrete their waste.

This routine happens throughout the course of the day.

Therefore, goldfish aquariums may require more frequent water changes, tank cleanings, and water tests than other fish species, but, it does not mean that they are toxic to other types of fish.

It should also be noted that without proper filtration, water changes, water tests, and tank cleanings that the tank water will become toxic to all inhabitants. 

One way to avoid this is to provide a large enough aquarium for each inhabitant to have at least 20-gallons of water.

For example, if you have five goldfish and a sucker fish then they should be living in an aquarium that is at least 120-gallons.

sucker fish

Water tests should be done regularly to control the nitrate, nitrite, and ammonia levels in the water

Water changes should be done at least bi-weekly, and tank cleanings may only need to be done as necessary (with a proper filtration system taking care of daily cleanings).

These basic steps can significantly reduce the amount of toxicity in a tank’s water, but this toxicity is not goldfish specific.

Myth #11: Goldfish cannot share a tank with tropical fish species

This is another example of a myth that has a little bit of truth in it.

Some types of goldfish cannot live with certain kinds of tropical fish. It is critical that you know which types should not be tank mates.

However, there are some tropical goldfish types that very well could be tank mates with certain goldfish types.

This is because some goldfish can tolerate water temperatures in the mid-70F degree range (which is high for most goldfish) and some tropical fish can tolerate the mid-70F degree range (which is low for most tropical fish). 

Mid-70F Degree Range

These fish may be able to share an aquarium. Although, other aspects may prevent this combination such as water conditions, habitat, type of fish, etc.

If you are considering placing goldfish and tropical fish in the same aquarium, then it is highly recommended that you do extensive research as well as speak with a fish expert to find out which species are inhabitable with each other.

Most goldfish owners believe that they have chosen a wonderful first-time pet that is low maintenance, doesn’t require too much responsibility, and will forget everything within a matter of seconds.


What they do not realize is that a properly cared for goldfish will live up to 50 years, remember things for up to 3 months, are high-maintenance, and will require drastically more responsibility than they ever imagined!

It is a choice that should be well thought out and researched before running out to your local pet store.

Be confident that you as well as your family is prepared for this life-long finned commitment!