Comet Goldfish look just like regular goldfish but with a much longer and more deeply forked tail fin!
The Comet Goldfish is also called the Comet-tail Goldfish or Pond Comet. This fish was the first variety of single-tail goldfish to be developed with a long caudal (tail) fin. It was developed in the United States from the Common Goldfish in the early 19th century, presumably by Hugo Mullert of Philadelphia, who then introduced them in quantity into the market.
Being a further development of the Common Goldfish, the Comet is sometimes confused for its close relative. The Comet Goldfish and Common Goldfish have an almost identical body shape. However, the fins on the Comet Goldfish are much longer, especially the caudal (tail) fin. Its caudal fin is also more deeply forked. On both these fish, the caudal fin is held fully erect.
The adult size of the Comet Goldfish is also smaller than the Common Goldfish. Yet they are every bit as durable and can be kept in either an aquarium or outdoor pond. Both fish are inexpensive and readily available.
The Comet is generally more reddish orange in color while the Common Goldfish is more orange. While the Comet Goldfish is typically a reddish orange, this fish is also available in yellow, orange, white, and red. They can also be found as a bi-color red/white combination, and occasionally they are available with nacreous (pearly) scales, giving them a variegated color.
Other types of Comet include the Sarasa Comet. This variety has long flowing fins and is characterized by a red-and-white coloration that holds a resemblance to a koi color pattern called ‘Kohaku.’ Additionally, the Tancho Single-tail Comet is a silver variety with a red patch on its head.
One of the hardiest of the goldfish varieties, Comet Goldfish are recommended for beginners. They are an easy fish to keep as they are not picky and will readily eat what is offered.
These fish can be quite personable and are delightful to watch. They are some of the most graceful of the elongated goldfish, and this quality is emphasized by their long tails. They are active, rapid swimmers and tend to leap out of the water occasionally, so having a lid on an aquarium is good idea. They are also very social and thrive well in a community.
Along with the other elongated goldfish, such as the Common Goldfish and the Shubunkin Goldfish, the Comet varieties make good pond fish. They are hardy and can tolerate cold water temperatures. They are moderate in size but are active and fast, so will get along well with Koi. Also, Comets usually won’t uproot plants, but they will readily spawn. Care should be taken, so they don’t quickly overpopulate your pond.
For more goldfish information, see:
Goldfish Care: Fancy Goldfish and Goldfish Diseases
- Kingdom: Animalia
- Phylum: Chordata
- Class: Actinopterygii
- Order: Cypriniformes
- Family: Cyprinidae
- Genus: Carassius
- Species: auratus auratus
- Aquarist Experience Level: Beginner
- Size of fish – inches: 4.0 inches (10.16 cm)
- Minimum Tank Size: 15 gal (57 L)
- Temperament: Peaceful
- Aquarium Hardiness: Very Hardy
- Temperature: 65.0 to 72.0° F (18.3 to 22.2° C)
- My Aquarium – Enter your aquarium to see if this fish is compatible!
Habitat: Distribution / Background
The goldfish of today are descendants of a species of wild carp known as the Prussian Carp, Silver Prussian carp, or Gibel Carp Carassius gibelio (syn: Carassius auratus gibelio), which was described by Bloch in 1782. These wild carp originated in Asia; Central Asia (Siberia). They inhabit the slow-moving and stagnant waters of rivers, lakes, ponds, and ditches feeding on plants, detritus, small crustaceans, and insects.
For many years, it was believed that goldfish had originated from the Crucian Carp Carassius carassius described by Linnaeus in 1758. This fish has a wide range across the waters of the European continent, running west to east from England to Russia, north to Scandinavian countries in the Arctic Circle and as far south as the central France and the Black Sea. However, recent genetic research points to C. gibelio as a more likely ancestor.
Goldfish were originally developed in China. The first goldfish were normally a silver or gray color, but early in the Jin Dynasty, somewhere between the years 265 – 420, breeders noted a natural genetic mutation that produced a yellowish-orange color. It became common practice to breed this pretty golden fish for ornamental garden ponds.
By the 1500’s goldfish were traded to Japan, to Europe in the 1600’s, and to America by the 1800’s. The majority of the fancy goldfish were being developed by Asian breeders. The results of this centuries-long endeavor is the wonderful goldfish colors and forms we see today. Domesticated goldfish are now distributed world-wide.
The Comet Goldfish was the first variety of the single-tail goldfish to be developed with a long caudal (tail) fin. It was developed in the United States from the Common Goldfish in the early 19th century, presumably by Hugo Mullert of Philadelphia, who then introduced them in quantity into the market. The Comet Goldfish is one of more than 125 captive-bred varieties of goldfish that have been developed.
- Scientific Name: Carassius auratus auratus
- Social Grouping: Groups – Can be kept singly or in groups.
- IUCN Red List: NE – Not Evaluated or not listed – There are no wild populations of this captive-bred variety.
The Comet Goldfish is an elongated, flat-bodied variety of goldfish. The head is wide but short, and its body tapers smoothly from its back and belly to the base of its caudal fin (tail fin). The caudal fin is long and deeply forked and generally stands fully erect. Comets have a natural life span of up to 14 years, though possibly longer if kept in optimal conditions.
The Comet Goldfish is a bit smaller than the Common Goldfish, but even so, the environment it is kept in will mostly determine whether your pet grows to its full potential size. In an average 15 gallon tank, if well cared for and not crowded, they can grow up to about 4 inches (10 cm), while in a larger, uncrowded tank, they can grow larger, generally reaching about 7 or 8 inches (17.78 – 20.32 cm). If kept in a spacious pond, they can reach over 12 inches (30+ cm).
They are primarily a reddish orange color, but they are also available in yellow, orange, white, and red. Some Comet Goldfish come in a bi-color red/white combination, and occasionally they are available with nacreous (pearly) scales, giving them a variegated color.
Comet Goldfish can and do naturally change color, but color changes are believed to be influenced by diet and the amount of light. Aquarists often report the reds and oranges of their goldfish changing to white. A fresh diet along with good lighting and available shade are suggested as the best ways to maintain the original coloration. Even so, these measures are not always successful.
Other types of Comet Goldfish include the Sarasa Comet. This variety has long flowing fins and is characterized by a red-and-white coloration that holds a resemblance to a koi color pattern called ‘Kohaku.’ The Tancho Single-tail Comet is a silver variety with a red patch on its head.
- Size of fish – inches: 4.0 inches (10.16 cm) – Comet goldfish housed in small aquariums will have stunted growth that will limit their size to four inches. In larger aquariums, they will reach about eight inches and up to twelve in a pond.
- Lifespan: 14 years – Comets have a natural life span of up to 14 years, though possibly longer if kept in optimal conditions.
Fish Keeping Difficulty
Comet Goldfish are some of the hardier species of goldfish. They are very undemanding of water quality and temperature. They can do well in a goldfish aquarium or even a pond as long as the environment is safe and their tankmates are not competitive.
Many people will keep goldfish in an aquarium with no heater or filtration, but for the best success, provide them the same filtration, especially biological filtration, that other aquarium residents enjoy.
- Aquarium Hardiness: Very Hardy – Take care that you invest in quality stock. Although Comets can be bought very inexpensively as feeder fish, this stock will often be disease-ridden and certainly not bred for longevity.
- Aquarist Experience Level: Beginner
Foods and Feeding
Since they are omnivorous, the Comet Goldfish will generally eat all kinds of fresh, frozen, and flake foods. To keep a good balance, give them a high quality flake food every day. To care for your goldfish, feed brine shrimp (either live or frozen), blood worms, Daphnia, or tubifex worms as a treat. It is usually better to feed freeze-dried foods as opposed to live foods to avoid parasites and bacterial infections that could be present in live foods.
- Diet Type: Omnivore
- Flake Food: Yes
- Tablet / Pellet: Yes
- Live foods (fishes, shrimps, worms): Some of Diet
- Vegetable Food: Some of Diet
- Meaty Food: Some of Diet
- Feeding Frequency: Several feedings per day
These goldfish are hardy and easy to keep in a well maintained tank. Minimum tank size is 15 gallons, so make sure water changes are frequent in such as small tank. Regular weekly water changes of 1/4 to 1/3 is strongly recommended to keep these fish healthy. Snails can be added as they reduce the algae in the tank, helping to keep it clean.
- Water Changes: Weekly – Goldfish produce more waste than most other freshwater fish and benefit greatly from more frequent water changes.
Setting up a goldfish aquarium in a manner that will keep your fish happy and healthy is the first step to success. The shape and size of the aquarium is important and depends upon the number of goldfish you are going to keep. These fish need a lot of oxygen and produce a lot of waste. Good filtration, especially biological filtration, is very helpful in maintaining the water quality of the aquarium. A filtration system will remove much of the detritus, excess foods, and waste, which keeps the tank clean and maintains the general health of the goldfish.
- Tank parameters to consider when choosing a goldfish aquarium:
- Tank size
Fifteen gallons is the absolute minimum required to house a Comet Goldfish. It’s best to start with a 20 – 30 gallon tank for your first goldfish and then increase the size of the tank by 10 gallons for each additional goldfish. Providing a large amount of water per fish will help dilute the amount of waste and reduce the number of water changes needed.
- Tank Shape
Always provide the maximum amount of surface area. A large surface area minimizes the possibility that the goldfish will suffer from an oxygen shortage. Surface area is determined by the shape of the tank. For example an elongated tank offers more surface area (and oxygen) than a tall tank. Oval or round tanks that are wide in the middle and narrower toward the top might be filled less than full to maximize the surface area.
- Number of fish
For juveniles a general rule of thumb is 1 inch of fish (2.54 cm) per 1 gallon of water. However, this rule only applies to young fish. Larger gold fish consume much more oxygen than young fish so maintaining this formula for growing fish will stunt them and could contribute to disease and even death.
- Fish size and growth
To allow for proper growth, either buy fewer fish than the maximum number or be prepared to get a larger tank. To prevent stunted growth and other health problems, don’t overstock the aquarium.
- Tank size
Goldfish are a cold water fish and will do best at temperatures between 65 – 72° F (18°- 22° C). The Comet Goldfish are one of the most hardy varieties and can tolerate temperatures a few degrees above freezing, as long as the cooling drops only a few degrees a day. A quick temperature drop can kill them, so if you live in a very cold climate, a heater is advisable.
Provide a gravel substrate to help create a natural and comfortable environment for your fish. You can add some decor, but make sure that all ornamentation is smooth with no protruding points or sharp edges. Smooth rocks or driftwood should be used sparingly if at all. Aquarium plants would be the best choice of aquarium decor for goldfish, but unfortunately, these fish are diggers. Consequently live plants may be uprooted. Artificial plants make a good substitute and silk plants are safer than plastic ones.
Most aquariums come with a cover that includes lighting. A cover for the tank is desirable as it reduces evaporation and though they are not prone to jumping, on occasion some gold fish will jump out. Lighting is not essential for goldfish, but does make the aquarium a nice showpiece and lighting will help if you have live plants.
- Minimum Tank Size: 15 gal (57 L) – Fifteen gallons is the recommended minimum to house this active fish. It has high oxygen requirements, produces a lot of waste, and will have stunted growth if it is kept in a smaller aquarium.
- Suitable for Nano Tank: Sometimes – A Nano tank is fine as long as it is 15 gallons or more. A larger tank will be needed for a community.
- Substrate Type: Any – A medium-sized gravel works best.
- Lighting Needs: Moderate – normal lighting
- Temperature: 65.0 to 72.0° F (18.3 to 22.2° C) – Goldfish can tolerate colder temperatures, but this is the optimum range for activity and longevity in Goldfish.
- Breeding Temperature: – In the wild, goldfish spawn in the spring when water temperatures reach about 68° F (20° C).
- Range ph: 6.0-8.0
- Hardness Range: 5 – 19 dGH
- Brackish: Sometimes – Goldfish are freshwater fish, but they have some tolerance for slightly brackish water. Any salinity for must be kept low, below 10%, a specific gravity of less than 1.002.
- Water Movement: Moderate
- Water Region: All – These fish will swim in all areas of the aquarium.
Goldfish are very social animals and thrive in a community. Not only are they a great community fish, but they are great scavengers as well. It is really not necessary to add other scavengers or other bottom feeders to the aquarium when you have goldfish.
Most fancy goldfish will thrive in both freshwater and tropical aquariums as long as there are no aggressive or territorial fish in the tank. Some good tankmates for fancy goldfish are the Chinese Blue Bitterling and the Northern Redbelly Dace. Comet Goldfish can be kept with other varieties of elongated goldfish, such as the Common Goldfish and the Shubunkin, and they also do fine with Koi.
- Venomous: No
- Temperament: Peaceful – Although rarely aggressive, Comet Goldfish are very active and might annoy tankmates that prefer a peaceful environment.
- Compatible with:
- Same species – conspecifics: Yes
- Peaceful fish (): Safe
- Semi-Aggressive (): Threat
- Aggressive (): Threat
- Shrimps, Crabs, Snails: Safe – not aggressive
- Plants: Threat – Goldfish will eat many kinds of aquatic plants. In their constant search for food, they can end up uprooting plants that they don’t eat.
Sex: Sexual differences
During the breeding season, the male has white prickles, called breeding tubercles, on its gill covers and head. Seen from above, a female will have a fatter appearance when she is carrying eggs. It is impossible to sex Goldfish when they are young and not in breeding season, but generally the male is smaller and more slender than the female.
Breeding / Reproduction
Comet Goldfish are egg layers that spawn readily in the right conditions. They can be bred in groups as small as five individuals, but they are very social animals and likely to breed in larger groups as well. The only time Goldfish will spawn in the wild is when spring arrives. To spawn them in the aquarium, you will need to mimic the conditions found in nature.
Provide an aquarium that is at least 20 gallons and make sure the fish are healthy and disease free. Some breeders suggest you treat them for parasites. Many breeders will also separate the males and females for a few weeks prior to breeding to help increase their interest in spawning. Introduce the fish into the breeding tank at the same time. The tank will need a lush environment with solid surfaces for the spawning process and for the eggs to adhere to. Bushy, oxygenating plants, such as Anacharis, work well for this, though artificial plants or fibrous spawning mops can also be used.
To induce spawning, the temperature can be slowly dropped to around 60° F (11° C) and then slowly warmed at a rate of 3° F (2° C) per day until they spawn. Spawning generally begins when the temperatures are between 68° and 74° F (20°-23° C). Feeding lots of high protein food such live brine shrimp and worms during this time will also induce spawning. Feed small amounts three times a day, but don’t overfeed. Uneaten scraps will sink to the bottom and foul the water. Maintain the breeding tank with partial water changes of up to about 20% per day.
Before spawning, as the temperature increases, the male will chase the female around the aquarium in a non-aggressive way. This can go on for several days, and the fish will intensify in color. During the spawn, the fish will gyrate from side to side, and the male will push the female against the plants. This stimulates the female to drop tiny eggs which the male will then fertilize. The eggs will adhere by sticky threads to the plants or spawn mop. Spawning can last two or three hours and can produce up to 10,000 eggs.
At this point, the parents will start to eat as many eggs as they can find. For this reason, it is best to remove the parents after spawning is complete. The fertilized eggs will hatch in 4 to 7 days, depending on the temperature. You can feed the newly hatched goldfish specialty fry foods until they become big enough to eat flake or brine shrimp, or you can offer the same food as you feed the parents as long as it is crushed very small. At first, the fry are a dark brown or black color in order to better hide and not be eaten by larger fish. They gain their adult color after several months and can be put in with larger fish once they reach about 1 inch long. See Breeding Freshwater Fish – Goldfish for more information on breeding Goldfish.
- Ease of Breeding: Easy
In properly maintained goldfish aquariums or ponds, goldfish illness is largely preventable. Even so, goldfish illnesses can occur, and if left untreated, may prove fatal. Goldfish are hardy, though, and if treated in a timely manner, most will make a full recovery.
When treating individuals, it is usually best to move the afflicted fish into a separate tank with no gravel or plants and do regular partial water changes. However, if the disease is apparent throughout the main tank, it may be best to do the treatments there. Whether treating in a hospital tank or your main tank, read and follow the manufacturer’s instructions for any medication. Some medications can adversely affect the water quality by destroying beneficial bacteria. You may also need to remove the carbon from the filtration system, as carbon will absorb many medications, making the treatment ineffective.
Goldfish diseases are mostly the same as those that afflict other freshwater fish, and the symptoms and treatment of goldfish are also similar. The main types of fish diseases include bacterial infections, fungal infections, parasites, and protozoa. There are also other ailments caused by injury, poor nutrition, or bad water conditions.
One of the more common problems is Ich, which is a protozoan disease. Ich is easy to identify because your fish looks like it is sprinkled with salt. Though Ich is easily treated, like other protozoan diseases, it can be fatal if not caught quickly. Some other protozoan diseases are Costia, which causes a cloudiness of the skin, and Chilodonella, which will cause a blue-white cloudiness on the skin.
External parasites are fairly common, too, but pretty easy to treat and usually not fatal when treated. These include flukes, which are flatworms about 1 mm long with hooks around their mouths. They infest the gills or body of the fish. Another type of parasite is fish lice (Argulus), flattened, mite-like crustaceans about 5 mm long that attach themselves to the body of the goldfish. Lastly, anchor worms look like threads coming out of the fish.
Some bacterial infections include Dropsy, an infection in the kidneys that can be fatal if not treated quickly. Fish Tuberculosis is indicated by the fish becoming emaciated (having a hollow belly). For this illness, there is no absolute treatment, and it can be fatal. Tail/Fin Rot may also be bacterial, though the reduced tail or fins can be caused by a number of factors as well. There is also fungus, a fungal infection, and Black Spot or Black Ich, which is a parasitic infection.
Swim Bladder Disease is an ailment indicated by fish swimming in abnormal patterns and having difficulty maintaining their balance. This can be caused by a number of things: constipation, poor nutrition, a physical deformity, or a parasitic infection. Feeding frozen peas (defrosted) has been noted to help alleviate the symptoms and correct the problem in some cases.
Other miscellaneous ailments include Cloudy Eye, which can be caused by a variety of things ranging from poor nutrition, bad water quality, and rough handling. It can also be the result of other illnesses, such as bacterial infections. Constipation is indicated by a loss of appetite and swelling of the body, and the cause is almost always diet. Then there are wounds and ulcers. Wounds can become infected, creating ulcers. Wounds can develop either bacterial or fungal infections, or both, and must be treated. There are treatments for each of these diseases individually and treatments that handle both. For more in-depth information about goldfish diseases and illnesses, see Goldfish Care; Fancy Goldfish and Goldfish Diseases.
The Comet Goldfish is inexpensive and readily available in fish stores and online.
- Animal-World References: Freshwater Fish and Plants
- David Alderton, Encyclopedia of Aquarium and Pond Fish , DK Publishing, Inc., 2005
- Marshall E. Ostrow, Goldfish (Barron’s Complete Pet Owner’s Manuals), Barron’s Educational Series, Inc. 2003
- Geoff Rogers, Nick Fletcher, Focus on Freshwater Aquarium Fish, Firefly Books. 2004
- David Sands, Goldfish (Caring for Your Pet), Interpet Publishing, 1999