breeds Comet Goldfish

Comet Goldfish Care Guide, Profile, Tank Conditions and Tankmates

Learn all about the comet goldfish, it’s breed profile, care requirements, tank setup, life expectancy and more.

Comet Goldfish are an incredibly popular variety due to the relative ease of feeding, keeping and caring for them in large home aquariums or ponds.

They’re a fantastic choice for the beginner fish-keeper, or even children under supervision. Extremely active, curious, hardy, large, and fun to watch and interact with, it’s little wonder they are one of the most popular goldfish varieties in the world today.

In this article, we take a deep look into the comet goldfish breed profile, discuss their ideal tank setup and environment, diet and feeding, tankmate compatibility and a few other interesting facts and figures.

And if you’re curious as to how they got their ‘Comet’ name, it’s because these single-tailed goldfish are fast and graceful swimmers.

Breed Profile and Summarized Care Sheet

Common name(s):Comet goldfish, sarasa comet.
Scientific Name(s):Carassius auratus
Origin:United States
Care Level:Easy to Intermediate
Temperament:Peaceful and social
Adult Size:10 to 12 inches
Color Form:Red, orange, yellow, white. Sometimes red/white. Tend to be more toward red side than orange.
Lifespan:5 to 15 years.
Minimum Tank Size:40 gallons, bigger is better, prefer to be in a pond.
Typical Tank Setup:Strong and efficient filtration, preferably planted, sand or gravel substrate to dig into, with good lateral swim space, so preferably wide tank, rather than tall.
Tank Level:All over
Water Conditions:Freshwater, 36 to 90 degress fahrenheit, KH 2 to 12, pH 6.8 to 7.2
Tank mates / Compatibility:Other single-tail goldfish, invertebrates, koi, minnows, african dwarf frog.


The Comet aesthetic is probably what comes to mind when most people think of goldfish – a long, streamlined body with a single tail.

Although they look similar to the Common Goldfish, Comets are easily discernible by their tails, which are heavily forked by up to 80%. The tail is at least the length of the rest of the body and can even reach double its length in some cases!

The rest of their fins are similarly long and flowing and the dorsal fin is always held erect.

A healthy specimen should have a bright metallic sheen and regular, even scales.

Comets are very common across the world and are readily available and reasonably priced from fish stores and online distributors, thanks to their prolific breeding habits.

Comet Goldfish Available Colors

comet goldfish in a planted aquarium with a gravel base

They are found in orange, yellow, white, olive and yellow-brown colors.

In comparison to their Common counterparts, coloration is generally more saturated and rich. For instance, orange Comets are often more deep red in tone compared to orange Commons.

Expertly bred Comets sport almost translucent pointed tail tips, contrasting with the deep colors of the rest of the body.

They cannot be calico-colored, according to the American Goldfish Association – this will be a long finned Shubunkin instead.

Colors can change and fade over time due to diet and exposure to light, and some people have even found their Comets fading to white. Good lighting and access to shade will generally prevent this from happening, however.

How Big do Comet Goldfish Get? – Average and Maximum Length

The maximum length for Comets varies according to their habitat: while those in a pond can grow up to 12 inches, larger aquariums will stunt their growth to around 8 inches and smaller aquariums to around 4 inches.

As they grow so large and are such fast and active swimmers, they are preferably kept in ponds and if you do keep them in an aquarium, buy the biggest you possibly can to allow them to reach their full potential.

How Long do They Live? – Average and Maximum Lifespan

They have an average lifespan of between 7 and 14 years with some living far longer if they’re kept in optimum conditions. 25 years isn’t unheard of!

These long lives can be attributed to their hardiness and the relative ease with which they can be cared for.

History and Origins

The Comet’s history and origins are disputed.

While some believe it was bred in Japan from the Common or Hibuna variants, others think it came to be by the crossbreeding of a mutated Ryukin and a Crucian Carp, while others still think it was bred from the Common Goldfish in the US in the 1880s.

If the Comet did originate in Japan, it would have come to the US by way of the World’s Fair, held in Chicago in 1893.

Are they Easy to Keep?

Their hardy disposition and low maintenance needs, do make Comets suitable for beginner fish keepers.

As long their water is kept clean, their environment safe, they are fed a varied diet of the right amounts, then they will thrive in an aquarium or a pond.

You could say this for any fish, sure. But it’s easy to do with Comets who are very forgiving when it comes to the odd fish keeping mistake , unlike some fancier types of goldfish.

Special Comet Goldfish Care Requirements

comet goldfish in a planted aquarium

In order to care for this goldfish properly, the biggest requirements are ample space, clean water and a varied diet. Though there, of course, other details to consider.

Avoid any aquarium equipment that introduces a strong current into their habitat – They are already fast swimmers.

Ensure there are no sharp edges or driftwood for your Comet to injure themselves with when choosing ornamentation for your aquarium. They can catch and tear their flowing tail and fins.

Diet and Feeding

They are omnivorous so are able to consume a mix of fresh, freeze-dried or flake foods with no problem.

Animal World recommend you feed them a flake food a few times every day as well as an occasional treat in the form of tubifex worms, brine shrimp, bloodworms or Daphnia, in order to ensure a varied and balanced diet.

Freeze-dried foods are preferable to live food as they eliminate the risk of introducing parasites and disease into your tank.

Tank Set-Up

Proper aquarium set-up is the first step to ensuring your Comet will thrive.

If you abide by the following guidelines, you can be sure of a happy and healthy fish who shall live for many a year.

Recommended Tank Size and Shape

Although the absolute bare minimum aquarium size is 15 gallons, we would recommend 30 to 40 gallons for the first fish, increasing by 10 to 12 gallons for each additional fish added.

Comets are notorious for producing a lot of waste so the more water there is, the more diluted their waste will be. And the bigger the tank, the more they can naturally swim and explore, keeping them fit and healthy.

When it comes to choosing the shape of the tank for your Comet, you need one with the maximum amount of surface area to ensure there is as much oxygen exchange into the water as possible.

Long, wide and shallow is the best tank shape to opt for. If you have an oval or a round tank, you can maximise surface area by ensuring you don’t fill it all the way to the top, but you should consider swapping it for a more suitable shape.

Do their Tanks Need Filtration?

The amount of waste created by Comets means you definitely require a filter in your aquarium – ideally one that filters at least six times the volume of water in the tank every hour.

Some incredibly skilled aquarists have planted set-ups without a filter but it’s not something I would ever suggest with a comet. They seriously MUST have their water filtered.

Substrate Requirements

Gravel substrate is great for mimicking a natural environment and will help bring out your Comet’s natural behaviors of rummaging and sifting through the stones looking for tasty morsels.

It’s also an easy and simple way to personalize your tank, to give it a little character and make it your own.

Do they Need Lighting?

Although not essential, a well-lit aquarium will deepen their colors, while also helping their bodies regulate with a contrived day to night cycle.

They will do fine without an aquarium light if they get to experience the natural ebb and flow of day and night in a room with windows (but out of direct sunlight!), but I prefer a well-lit aquarium and to be able to see my fish colors pop.

Preferred Water Temp?

Comets are hardy and can withstand very cold temperatures, providing that such temperatures are consistent. While they can withstand even a few degrees above freezing, a sudden temperature drop can be fatal.

Somewhere between 65 to 72 degrees, Fahrenheit is optimal for these cold-water fish so a heater may be necessary if you live in a very cold climate, and cooling may be required if you live somewhere very warm.

Video: Comet Goldfish (and Sarasa) in A Pond

To see these beautiful fish in action, please see the video below. You’ll notice they are very active, fast swimmers, curious, have nice long flowing tails and are wonderful to look at.

Compatibility With Other Fish

Comets are social creatures and thrive as part of a community although they can be kept alone if necessary. It’s normal for beginner fish keepers to start with just one and add more once they’re acquainted with how to keep them successfully. Just ensure that you don’t overstock the pond or tank!

Although they are peaceful fish, they are highly active swimmers who eat a lot and can occasionally nip on other less hardy variants of their species. As such, they’re best kept in a tank with other Comets or the similar single tail Common who can keep up and compete with them.

Avoid keeping them with fancy or very fancy goldfish variants who might suffer at the hands of Comets.

However, they do have promising compatibility with Koi and White Cloud Mountain Minnows. Bear in mind that the latter are shoaling fish, however, so will need to be kept in a group of at least five, requiring a substantially sized tank or pond.

They are also compatible with shrimps, crabs, snails and African Dwarf Frog.

Comets will eat or at least uproot plants due to their innate digging instincts so it’s best to select plants highly suited to goldfish tanks, or to settle for silk, artificial plants if you are set on including plants in your aquarium as a beginner.

We’re not saying you can’t have live plants – just that they are harder to maintain in a tank with comets. Though many people are successful with the right selection of plants and their needs. It just takes more work and skill.

Final Thoughts

The comet is close to what most people imagine when they to picture a goldfish. Long, slender, a single tail and long flowing fins.

They can grow large, so do best in a pond or very large aquarium where they’ll be able to stretch out and dart about quickly as their bodies are designed to do.

They are easy to keep, making them great for beginners, and due to the size they grow and highly active lives they lead, they are a pleasure to own and look at.

If you have anything to add, or any questions or feedback, please feel free to drop them in the comments, we will answer every one.

Jeremy is the chief editor of this site. A fish keeping enthusiast for more than 2 decades, he founded this site so he can share his knowledge with others, to aid in enjoyment of fish keeping, and to get as much fun out of the hobby as he does.

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