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Comet Goldfish Care, Information, & Pictures (Breed Guide)

Comet Goldfish are a type that few serious aquarists consider with the endless varieties of goldfish out there. But I personally feel that these are some of the most desirable goldfish to care for!

Comet Goldfish are significantly hardier than Orandas and other fancy breeds. They thrive in outdoor ponds, grow quite large, and will readily breed in either aquariums or ponds. Let’s get to know the Comet Goldfish!

What Are Comet Goldfish

What are Comet Goldfish?

With the intense metallic color of its flanks and long, deeply forked tail, it’s easy to see how the Comet Goldfish gets its name! But where do these Goldfish originate?

Most aquarists know that China is the original homeland of all Goldfish. These East Asian carp were bred in ponds for thousands of years to provide food for the cities and villages of the region.

However, a few gold-colored individuals were discovered one day lost to antiquity. These beautiful, seemingly lucky fish were carefully raised and bred, passing on their golden genes. From them come all of the Goldfish in today’s aquarium world.

Comet Goldfish and Common Goldfish

Most Goldfish breeds are of Asian origin; the Chinese and Japanese are especially good at breeding local varieties like the Japanese Ryukin and Black Moor. However the Comet is actually quite recent as far as Goldfish lineages go!

They have their roots in the United States, of all places. Hugo Mulertt, a government worker, developed the breed in the 1880’s from the Common Goldfish line. Comet Goldfish are essentially a Common Goldfish with a long tail fin.

While not as different in form as Orandas or Moors from their wild roots, the Comet was and is still recognized as a distinct breed of Goldfish! And their long tails have been passed on to many other distinct breeds, such as the Shubunkin Goldfish. So how do we care for these shapely, long-tailed Comets?

  • Common Name: Comet Goldfish, Sarasa Comet Goldfish, Black Comet Goldfish, White Comet Goldfish
  • Scientific Name: Carassius auratus
  • Origin: United States
  • Length: 8-20 inches
  • Aquarium Size: 30 gallons
  • Temperament: Peaceful
  • Ease of Care: Very Easy

Sarasa Comet Goldfish

Sarasa Comet Goldfish are a little more special than most other comets. They look similar to a white Comet Goldfish except Sarasas have red patches along their flanks as well. If you are familiar with Koi Varieties then the Kohaku would be the koi version of a Sarasa Comet as it has the same base white with red color!

Sarasa Comet Goldfish are a Chinese breed and have precisely the same care requirements as any other Comet Goldfish. They are very hardy and will long for a long time when well cared for! While Black Comet Goldfish, White Comet Goldfish, and other Comet Goldfish colors are very desirable, few can compete with the Sarasa!

Comet Goldfish Care

Comet Goldfish Care

Comet Goldfish Tank Size

Goldfish are pretty sizable fish and Comets are no exception. In fact, they are larger than the average fancy Goldfish are pretty sizable fish and Comets are no exception. In fact, they are larger than the average fancy Goldfish, capable of growing as large as their wild ancestors. A full grown Comet Goldfish can grow up to 20 inches.

Unfortunately, Comet Goldfish might be the breed most likely to end up in a bowl. They get mixed in with Common Goldfish as cheap feeder fish or end up at fairgrounds as carnival prizes. These Goldfish inevitably end up dying very young and far smaller than what’s possible for them.

How long Do Comet Goldfish Live For?

Full grown Comet Goldfish will live for decades if well taken care of and will reach 6-8 inches by 2-3 years of age! Therefore, you should be thinking about a long-term tank, not a small, short-term solution that you will upgrade later. Given how large they can grow, a 30 gallon aquarium is the absolute minimum for an adult Comet Goldfish care.

I recommend getting an even larger aquarium if they continue to grow. Or better yet, move them to an I recommend getting an even larger aquarium if they continue to grow. A full grown Comet Goldfish will find a 55 gallon tank ideal for its needs, especially if kept with a few of their own kind. Or better yet, move them to an outdoor Comet Goldfish pond where they can swim free of walls and graze on the abundant algae and insects that thrive in ponds!

Comet Goldfish are also one of the most winter-hardy breeds. In temperate countries like the United States they will have no trouble overwintering by hibernating. So long as the water is at least a few feet deep in part of the pond, that is. But as young fish they will do just fine in aquariums as small as 10 gallons. Just be ready to upgrade in a few months and spend more money.

Comet Goldfish Water Conditions

Comet Goldfish are famously tolerant of a wide range of water conditions. This is because carp are accustomed to living in foul, still waters that other fish can’t tolerate. In this respect they are like aquatic pigs, which is why they are so popular to raise as food fish around the world.

Do Comet Goldfish Need a Filter?

That said, just because they can live in stagnant water doesn’t mean that you should give that to them. A filter for your Goldfish provides water flow, helps break down nitrogenous waste (ammonia, nitrite, nitrate) into harmless byproducts, and ensures oxygen and carbon dioxide exchange happens naturally.

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Comet Goldfish can tolerate slightly elevated ammonia levels but they may show black patches, red burns, and other signs of stress. Instead, we should strive to keep toxic chemical levels as close to 0ppm as possible. Be on the lookout for excess nitrates as well. In established fish tanks where aquarium maintenance grows lax, nitrate levels can creep up unexpectedly. This can cause brown gills, excess mucus production, and death, even in hardy Comet Goldfish.

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Comets are very versatile when it comes to water chemistry as well. They do just fine in slightly acidic to alkaline conditions (pH 6.0-7.5+) but are happiest in alkaline to neutral water (pH 7.0).

Do Comet Goldfish Need a Heater?

Comet Goldfish are also tolerant of a wide range of water temperatures. Unlike fancy Goldfish, Comets don’t need a heater. In fact, temperatures above 75℉ tend to stress them out. Warm water jump starts their metabolism, causing them to eat more and poop more. They also grow faster but live shorter lives in the process and are more prone to disease. Instead Comet Goldfish should be kept at room temperature or cooler for best health.

Large Comet Goldfish are some of the best outdoor pond fish. They acclimate quickly to being kept outside in temperate climates. They will also overwinter in deep ponds, going into torpor until the spring melt comes.

Torpor is similar to hibernation except it’s more like a deep sleep that can be interrupted at any time when the weather gets warm enough. But if things get cool again the fish will re-enter torpor with no problems. Hibernation is more efficient for energy conservation but also much less flexible and riskier to an animal to enter and come out of early. So animals that truly hibernate tend to live in far northern regions where they can expect to remain in hibernation for months at a time.

Even if the pond ices over, so long as a hole is kept open in the ice for gas exchange, your large Comet Goldfish will remain in torpor until spring (and mating season) arrives. If the pond freezes over this can be very dangerous because oxygen and carbon dioxide are no longer able to enter and leave your Comet Goldfish pond.

In nature the water volume is so large that it matters very little. But in your home outdoor Comet Goldfish pond there is far less oxygen to go around.

Comet Goldfish Plants and Substrate
Сomet or comet-tailed goldfish (Carassius auratus) in natural aquarium

Comet Goldfish Plants and Substrate

Comet Goldfish are easy to care for in most respects. But they can be a little rough on your plants and substrate. Goldfish simply love to dig and spend most of their time either begging for food or looking for it along the bottom.

As they dig they disturb plant roots constantly, which plants hate. And they dig little pits that mess up the look of your aquascaping. In short, Comet Goldfish have rather poor manners so you’ll need to plan a bit for their bad habits.

If you really want to use live plants in your Goldfish aquarium try giving the plants a month to get solidly established. Or buy your Comet Goldfish while they are too small to do too much damage. That way, as the Goldfish mature the plants will have developed strong root systems that will withstand the occasional Comet Goldfish storm of activity!

Plants with thick root systems include Amazon Sword plants and Vallisneria. Be careful when buying soft leaved plants like Anacharis and Cabomba because Goldfish find them absolutely delicious! They will likely be uprooted and eaten by a large Comet Goldfish.

Also take time to decide on whether you want to go with sand or gravel. Sand is beautiful but your Comet Goldfish will sometimes leave deep pockets where they’ve decided to dig and find food. Gravel is harder for them to lift about and the holes self-fill much more often than sand.

Comet Goldfish Tank Mates

As peaceful as all Goldfish are, Comets are fairly easy to match with other fish. The main issue to choosing good tank mates is temperature. Comet Goldfish are cool to coldwater fish and won’t do well alongside Angelfish, Gouramis, Tetras, and other tropical community fish.

Instead, try Livebearers (Guppies, Mollies, Swordtails, etc), larger Barbs like Tinfoil and Eight Striped Barbs, Danios, and other cold-tolerant species. Dojo Loaches are popular to keep alongside Goldfish.

Koi might be some of the best pond mates for a Comet Goldfish pond. These larger cousins to Goldfish come in several varieties that are bred to be best appreciated from a top view. The graceful form and flowing tails of Comet Goldfish make them great additions to any Koi pond. While smaller, they are very closely related carp and have nearly identical care requirements.

The only fish you need to really watch out for are aggressive tank mates. Cichlids, large Catfish, and other territorial bottom dwellers can make things very difficult for Comets. Goldfish don’t really understand what a “territory” is and will be constantly nipped by these fish.

Good Comet Goldfish Tank Mates

  • Barbs, Danios, Koi, and other Cyprinids
  • Livebearers (Guppies, Mollies, Platies, etc)
  • Dojo Loaches
  • Chinese High Fin Sharks
  • Other Goldfish

Poor Comet Goldfish Tank Mates

  • Gouramis, Tetras, Angelfish, and other warm water tropical fish
  • Cichlids, large Catfish, and other territorial fish
  • Small invertebrates (shrimp, snails, etc)

What Do Comet Goldfish Eat?

Comet Goldfish are very easy to feed because if it hits the water they are likely to try it! While you may know folks that offer their fish bread to eat, I strongly advise against feeding your fish human food.

That said, Comet Goldfish are omnivores just like us! That means they need a healthy balance of plant and animal matter to thrive. Stick to a slightly vegetarian bend for your Comet Goldfish: boiled vegetables like spinach, squash, and peas are great treats for them. Prepared foods rich in vegetables like spirulina powder are also inexpensive and even more convenient.

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Comet Goldfish also need some animal protein, though. So be on the lookout for worms, insects, and small snails to toss in the aquarium.

If you have Ramshorn Snails the adults are often large enough not to be eaten while providing a regular source of tasty baby snails for your Goldfish to eat. Frozen or live brine shrimp, blood worms, earthworms, and tubifex are all favorite foods of theirs also!

How to Breed Comet Goldfish

Comet Goldfish breeding is quite easy to do so long as you have healthy, well-fed Comets. Pond breeding is much easier as Goldfish prefer spawning in tangled plant thickets. An outdoor pond also provides enough room for full size Comet Goldfish to find mates and spawn where they please.

Also, they respond to seasonal variations in temperature to know when to spawn. Goldfish spawn in the late spring to early summer once the ice has melted and they have had time to rebuild their fat reserves.

Indoor aquariums typically stay constant in temperature year-round, which can complicate matters. Still, you can simulate a change in seasons with a heater and some patience!

Sexing Goldfish isn’t easy either. But Comets and other breeds that are close to the wild variety are easier than fancy Goldfish in this respect. Once your Comet Goldfish are sexually mature (5-6 inches), the females will plump up slightly. This is usually more obvious from above than side viewing.

Males also develop what are called breeding tubercles on their gill covers and heads. These bony lumps signal that he’s hormonally charged and ready to spawn!

Females may develop a few as well but never as many as an adult male. The male will also start chasing females he senses are close to being ready to spawn, helping you identify your females.

All Goldfish are egg scatterers. In nature, they spawn in thick tangles of weedy plants near the shore. Their eggs are sticky and adhere to whatever they touch. The adults then leave the eggs and fry to their own devices.

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Unless you’re keeping dense plants like Hornwort for them to spawn in, you’ll want to add a plastic spawning mop for your Comet Goldfish eggs. Otherwise they will eventually find and eat their own eggs and fry. You can then remove the plants the eggs were laid on to a fry rearing tank.

Once the eggs hatch, the young Comet Goldfish lie motionless for 3-7 days, absorbing nutrients from their yolk sacs. Once they start swimming freely, you know they are ready to begin feeding.

The best food by far for them is live brine shrimp nauplii but they may accept frozen nauplii, daphnia, or powdered fish flakes. From there, you simply need to keep the water clean and watch as they slowly mature into young adult Comet Goldfish!

Frequently Asked Questions about Comet Goldfish

How Big Do Comet Goldfish Get?

A full grown Comet Goldfish will be anywhere from 8 to 12 inches in length. This means that they should only be kept in aquariums of 40 to 55 gallons when they are this large. But smaller Comets can be kept in small aquariums so long as you are ready to upgrade when the time comes!

Are Comet Goldfish Good Pets?

Comet Goldfish are beautiful, hardy, and long lived pets. They are also very resistant to poor water conditions and will eat anything you feed them. They are one of the best pet fish you can give to children and other beginning aquarists!

How Long Can Comet Goldfish Live?

Comet Goldfish are very long lived aquarium fish. They will live a few decades if well cared for; believe it or not, 20 to 30 years is an average lifespan for a goldfish! The longest lived pet goldfish was Tish, a carnival goldfish that lived to be 43 years old!

Do Comet Goldfish Need to be Kept in Pairs?

Comet Goldfish have no special need for being kept in pairs. But it is better to keep two or more goldfish rather than just one. Goldfish are not schooling or shoaling fish but they do interact with each other and enjoy the stimulation. You are also more likely to witness them breeding when you keep more than one or two Comet Goldfish together!

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

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