The Goldfish
By Sarah Screen

Copyright © Practical Fishkeeping

Common Name :

Scientific Name :
Carassius auratus

Family :

Geographical Distribution :
Goldfish are the domesticated version of the Gibel Carp.

Although wild populations have been recorded as far West as Eastern Europe the Gibel Carp is native to Eastern Asia.

Its natural environment consists of well vegetated ponds and lakes, however, its great versatility means that successful breeding populations have been observed in habitats ranging from fast running rivers to stagnant ditches.

The Gibel Carp was first domesticated in China around 800 AD and many of the varieties that we see today are due to Chinese breeders. It wasn’t until the late 17th century that the domesticated Goldfish became widespread throughout the Far East and was first introduced into Europe.

Goldfish Varieties :
All Goldfish belong to the same species, however within this species there are many varieties or breeds. Each variety can be further broken down into strains referred to by breeders as variants.

There are over 100 variants of Goldfish that are officially recognised for show purposes, and due to the fact that all varieties can interbreed there are potentially countless other “unofficial” variants living in aquaria around the world.

Below are the main categories that breeders use to classify Goldfish. There are numerous variants of Goldfish under each heading – and some variants that could arguably sit under two or more headings, for example, some of the dorsal-less varieties are now being bred to include a dorsal fin.

A certain amount of controversy surrounds the more unusual variants. Some consider the characteristics that they are prized for to be deformities which inhibit the fish’s ability to swim and feed and very possibly shorten the fish’s lifespan. Whatever your opinion, it is fair to say that varieties such as the Celestial and Pompom are certainly an acquired taste.


Adult Size


Single Tailed Goldfish

Common Goldfish


The closest form to the Gibel Carp from which all Goldfish are descended.
Also bred as “feeder goldfish” as a food source for larger carnivorous fish.



Very similar to the Common Goldfish, but with long flowing fins.



A calico version of the common goldfish. The name is derived from the Chinese “Chuwen Chin” meaning “poor man’s Koi”.

“Fancy” Goldfish
Characterised by a round egg-shaped body and a double tail, the Goldfish referred to as “fancy” are all descended from the common single tailed goldfish.

Double Tailed “Fancy” Goldfish



A basic egg-shaped Goldfish with a double tail that was first recorded during the Ming Dynasty in the 1400’s. This is the original “fancy” goldfish from which all other fancy varieties have been derived.



The distinguishing feature of the Oranda is its Wen or Headgrowth.



The protruding eyes of these fish give this variety its name. One of the most widely available telescope variants is the Black Moor.



Characterised by its dorsal hump, the Ryukin is an unusually tall variety, requiring a deeper tank than other fancy varieties.



Pearlscales are a relatively new variety developed in the late 1800s. Their scales contain high deposits of calcium carbonate giving them a distinctive raised and translucent quality.



In the Tosakin the double tail is not divided and forms a perfect semi-circle. For this reason Tosakins are also known as “peacock goldfish”.



An exception among the fancy goldfish varieties, Wakin’s do not have an egg-shaped body. Developed by breeders in Japan, where the natural elongated body shape is highly prized, these fish resemble a fan-tailed Koi.

Dorsal-less “Fancy” Goldfish



This is the common ancestor to all the Dorsal-less breeds available today and resembles the basic Fantail minus the Dorsal Fin.



Originating in China in the 1600s the Lionhead  is one of the oldest of the dorsal-less breeds. The most well-known variant is probably the Ranchu – one of the most expensive Goldfish available in the world today.



Also known as “Stargazer Goldfish”, this is a variation on the Telescope, lacking a dorsal fin and with eyes that are turned upwards so that the fish is perpetually staring at the sky.



Similar to the Celestial but with the addition of two fluid filled sacs – one under each eye.

Pom Pom


This variety has large fleshy nasal outgrowths, referred to as pompoms, which in some variants can actually descend past the fish’s mouth.

Note regarding Goldfish sizes:
The sizes that I have quoted are the expected size of an average adult fish kept in good conditions, based on my own experience and on that of other Goldfish keepers. There are recorded instances of both single tailed Goldfish and Oranda far exceeding these sizes (even to the 16” mark) so be aware of the potential of these fish to grow huge.
The fancy goldfish on sale at local fish shops are unlikely to be pure breeds, so unless buying from a specialised breeder, it is possible that the fish may not conform exactly to the characteristics above.

Water Parameters :
Goldfish are relatively undemanding fish. In a home aquarium a temperature of between 18 and 21 degrees, medium to hard water and a PH of over 7.2 is ideal. However, they can be successfully acclimatised to a PH range of between 6.0 and 8.5 and will tolerate temperatures of between 1 and 30 degrees, also making them suitable candidates for ornamental fish in garden ponds.

Below 10 degrees, the Goldfish’s metabolism slows down so that it will have difficulty digesting food. At this sort of temperature only wheatgerm based foods which are easily digestible should be fed.

Below around 6 degrees the Goldfish will stop eating altogether and enter a period of dormancy. They can overwinter in this condition even if the surface of the pond freezes over, provided that there is still sufficient oxygen in the water. (Their oxygen consumption is seriously diminished during their dormant phase)

At the other end of the scale Goldfish will start to struggle with the oxygen levels at temperatures above around 24 degrees, and will require additional aeration within this temperature range.

Both the single-tailed Goldfish and the basic Fantail are incredibly hardy and can endure very poor water quality. That is not to say that it is acceptable to keep them in these conditions, but it does make them a good first fish as they are very forgiving of any errors the novice fish-keeper may make.

As the extent of the modifications to the breed increases, however, so they become more susceptible to water quality issues. Goldfish such as the Pompom and the Bubble-eye are extremely sensitive and will deteriorate very quickly if high water quality is not maintained.

 Tank Requirements :
Contrary to the iconic image of a Goldfish in a bowl, Goldfish actually require a large amount of space in an aquarium. They have a high oxygen requirement, produce a great deal of waste and need a lot of swimming space. A good filtration system is also essential to deal with the quantities of waste produced.

For this reason, I believe that the large single tailed Goldfish varieties are generally unsuitable aquarium inhabitants and are really far better suited to ponds.

Conversely, many of the fancy varieties are unsuitable pond candidates. Their slower swimming speed makes them vulnerable to predators and many of them are too sensitive to withstand the temperature fluctuations that will occur in an outdoor setting.

Many numbers are quoted as to the minimum amount of space required for Goldfish, ranging from 8 gallons to 15 gallons per fish. A more useful rule of thumb may be to allow a gallon per ½” of adult fish. This allows for the variation in size between the different varieties, and a 6” fish would equate to a requirement of 12 gallons – about the mid-point between the commonly quoted sizes.

Equally important is the shape of the tank. Tall, thin tanks are not suitable for goldfish, the ideal being a long, shallower tank. This has the dual benefit of providing a large surface area to maximise the amount of oxygen in the water and of allowing the Goldfish to swim the long lengths that they require in order to exercise properly. As a minimum a Goldfish should be able to swim 6 times its body length in the aquarium.

A well fitting lid is essential as Goldfish can be jumpers, and although they will enjoy a planted tank only very hardy plants are suitable. Goldfish will reduce many plants to mere skeletons within hours and can uproot even the hardiest plants from the substrate.

Tank Mates :
Although they will interact with other fish, Goldfish do not need to shoal in the same manner as species such as Tetras, and can therefore be kept as a single specimen with few problems. The addition of tank mates, however, will increase their confidence levels and allow their natural behaviours to be observed at their best.

Different variants of Goldfish can be combined together and will make for a stunning display. However, it is not wise to mix single tailed and fantailed variants as the faster swimming single tailed fish will outcompete the fantails for food. The same is true of mixing dorsal-less variants with their dorsal finned cousins.

There is no ideal number of Goldfish to keep in an aquarium, and the decision is usually driven by the space available. The traditional number for an aquarium is 3, however this is based on the principles of Feng Shui (the mix being 2 gold coloured fish and one black fish) rather than on any real benefit to the fish.

Smaller shoaling fish such as White Cloud Mountain Minnows and certain Danios will thrive in similar aquarium conditions to Goldfish. They should however only be added with caution. Goldfish will eat anything that they can catch and that is small enough to fit into their mouth, while faster swimming small fish may outcompete the Goldfish for food.

 Feeding :
Goldfish are omnivorous and ravenous eaters. It is not unheard of for Goldfish to gorge themselves to the point where their stomach ruptures, so portion control is essential.
Generic flake or pellet foods provide a good basic diet, but Goldfish will appreciate supplements of fresh vegetables and protein rich foods such as bloodworm. Live food, when available, will be eagerly accepted.
Breeding :
In an outdoor environment it is the change in temperature from the long cold spell over Winter to the warming of the water in Spring that triggers breeding. As most indoor aquaria are at a fairly constant temperature all year round it is unusual, but not unheard of, for breeding to occur.

In ponds and in aquaria where this temperature fluctuation has been replicated (either deliberately or by accident) Goldfish will breed easily and prolifically, with up to three spawnings occurring in a single season.

Outside of breeding season, it is very difficult to sex Goldfish. Females tend to have a deeper rounder body and be substantially larger than males. However, as most fancy varieties are bred for a rounded body shape and due to the amount of cross-breeding between different sized variants it is often impossible to make the distinction.

During breeding time the female Goldfish will become noticeably swollen around the lower abdomen as the eggs develop while the male will develop tiny white pimples known as tubercles around his head and gill plates. Depending on the maturity, variant and colouring of the male these may or may not be visible to the naked eye. If they are visible, they can easily be mistaken for whitespot or ich and many Goldfish have endured unnecessary medication at this time.

Goldfish exhibit none of the elegant courtship rituals of some other species of fish - their courtship is brutal and often violent. The male will tirelessly pursue the female, attempting to press the tubercles against her abdomen to stimulate the release of the eggs, often driving her down to the bottom of the aquarium or pond and pinning her to the substrate. There will be a great deal of thrashing around and injuries such as torn fins, lost scales and minor abrasions are commonplace.

This behaviour can last for several days but is necessary in order for the female to release her eggs. Do not separate Goldfish at this time, no matter how distressing the behaviour appears, as without this attention the female may become eggbound with possibly fatal consequences.

Once the eggs have been released and the male has fertilised them, both Goldfish will lose interest in each other. It is important to be vigilant for diseases and illness at this time. It is an exhausting process for both fish, often they will not eat at all during this period and there is a high chance of infection in any wounds. This is one of the only times when I would advocate using a broad spectrum anti-bacterial as a preventative measure.

Goldfish make exceptionally poor parents. After all the effort of breeding they will readily devour both eggs and any fry. Fortunately they are extremely prolific breeders, producing hundreds (some claim thousands) of eggs at each spawning, so even without any special care some fry usually survive into adulthood.

Unusually for a species that drives females so hard at breeding time, the recommended ratio for breeding is 2-3 males per female.

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