Comet Goldfish: Ultimate Guide (Care, Diet, Breeding & More)

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Written By Matt Stevens

Hi, I'm Matt! I've been obsessed with fishkeeping for over 15 years now and created this site to share my knowledge with others.

Comet Goldfish are an ever-present species in the aquarium community for a good reason. For many aquarists, nothing compares to this fish’s ease of care, vibrant coloration, and beauty.

But with their hardy nature, it’s easy to ignore some of the most significant aspects of Comet Goldfish care. That’s why this guide will break down everything you should know to keep healthy and happy Comets at home.

Precisely, it will cover the fish’s lifespan, size, general appearance, tank size, diet, behavior, tank mates, breeding, and more!

Species Overview

The Comet Goldfish is a constant figure in the aquarium community, and their delicate tank requirements make caring for them even more interesting. 

Lifespan10-20 years
Care LevelEasy/moderate
Behavior & TemperamentPeaceful and playful
CompatibilityOther goldfish varieties
Food and DietOmnivores
SizeUp to 12 inches
Tank SetupFreshwater, cold, planted
Tank Size (Minimum)50 gallons

A quick background check shows that these fish were first kept in the USA, with Hugo Mulertt credited with their increasing popularity in the 1880s. Ever since, these fish have been captive-bred for almost a century.

In the modern fishkeeping community, these fish are sometimes called the Comet Tailed Goldfish, with the scientific name Carassius auratus.

Today, Comet Goldfish have grown in popularity and admiration to become a staple figure in the aquarium community. If you are looking for the missing piece of the puzzle to complete your aquarium, this magnificent Goldfish variety will warm your heart.

Like many varieties of the Fancy Goldfish, the Comet Goldfish are no longer available in the wild. You can only find them in local fish farms and pet stores where they are captive-bred for sale.

Just like their ancestors, Comet Goldfish have simple care requirements, despite their rarity in the wild.


Comet Goldfish will turn out to be a smart investment if you consider their long lifespan. Keeping them at home requires sheer commitment over a long period because they can live for 10-20 years.

The lesser-known secret about increasing the fish’s lifespan is sustainable tank water conditions and ample swimming space.


Comet Goldfish are exactly what they sound like. A beautiful freshwater fish with distinct tailfins that are magnificently positioned during swimming, hence the “comet” name.

The first striking feature you will see in the Comet Goldfish is their exceptional body shapes. But if you can’t separate them from the standard Goldfish, the forked tails should guide you in choosing the Comet variety.

The Comet Goldfish’s single tails only have two tips, and the large dorsal fin completes their splendid look. Conversely, the anal fins appear thinner than in many species and will combine perfectly with the two long pectoral fins when the fish is darting around.

What’s more, Comet Goldfish have semitransparent fins, which may sometimes assume the general body coloration.

You will have plenty of options to choose from regarding the general body coloration. We’ve seen Comet Goldfish of yellow, red, white, and orange variants, as well as the rarer brown species.


Assuming they have pristine conditions at home, a full-grown Comet Goldfish will be up to 12 inches long. They enjoy a steady growth rate, and the juvenile fish you will purchase from the local pet store won’t take long to reach full maturity.

Also, Comet Goldfish growth rate is an important determining factor when setting up their habitats at home.

With all that said and done, never forget that the Comet Goldfish’s average size will depend on the tank conditions and actual environment. Poor water quality is the fastest way to limit their growth rate even when the tank size is perfect.

Interestingly, some versions have claimed that a Growth Inhibiting Hormone influences the Comet Goldfish’s growth rate in maturity. Precisely, it is believed that the actual effects of this hormone will depend on the nature of the tank.

Accordingly, these fish will appear bigger if kept in larger tanks and show a similar pattern in smaller habitats.

Comet Goldfish Care

For some reason, Sarasa Comet Goldfish care has never been clear to many aquarists. Perhaps the biggest fallacy is that caring for Comet Goldfish will be a piece of cake just because they are moderately sized fish. But that’s far from the truth.

These are hardy fish that will happily adapt to the existing conditions inside the aquarium. But the better you understand their care needs, the easier it will be to create the ideal environment.

Unlike most tropical fish species, Comet Goldfish want cooler conditions to survive in home aquariums.

The next paragraphs will give you handy information about Comet fish care in captivity.

Tank Size

As a committed aquarist, nothing will give you as much satisfaction as seeing your fish thrive inside the home aquarium, even when you have just a small tank.

And for Comet Goldfish, the smallest tank size should have a 40-50 gallon capacity. Ideally, a 75-gallon tank would be excellent for the fish’s health and comfort.

The funny thing about the Comet Goldfish is that they have a steady growth rate that amazes many aquarists. So, the worst mistake you must avoid is restricting these fish to a small space throughout their lives.

Even if you have a smaller tank for a start, be sure to set up the right size before your fish approach puberty. Again, the hormonal concept should guide you when designing the right tank.

A handy guideline states that you should add a further 50 gallons for every additional Comet Goldfish you introduce to the aquarium. But if you can’t keep up with their tank requirements in captivity, consider an outdoor pond to accommodate the entire community from the onset.

Water Parameters

What would a Comet Goldfish’s ideal home look like? Well, if you are unsure about the right tank conditions for your Comet Goldfish, you may want to take a leaf from wild Carp. Or, just get it from us!

As a team that has kept both wild Carp and other Fancy Goldfish varieties, here are our recommendations for the ideal tank water parameters:

  • Water hardness: 5-19 dKH
  • Water temperature: 65°F-70°F
  • pH levels: 6.0-8.0

Generally, you should ensure the tank water conditions are well suited to the Comet Goldfish’s needs. You can achieve this by measuring the water status frequently using a suitable aquarium testing kit.

What to Put in Their Tank?

Interestingly, Comet Goldfish create the perfect bonds with their owners, and some reports have proven that they can recall the aquarist and master their environment quickly.

They will like it more if you readjust their environments occasionally to capture their attention. You can start with well-sized gravel for the ideal substrate in terms of tank decorations.

Also, rock caves and plastic decorations will do the trick for natural or artificial hiding spots.

Natural plants should be an automatic addition to the Comet Goldfish’s habitat to provide important food sources and help with proper aeration.

However, choosing between floating and rooted plants will be a personal decision, and you can only make the best guess after trialing both options. Nevertheless, java fern, hornwort, and anacharis are some of the best options to start with.

If you need more options to maximize oxygen supply, you should consider air bladders, waterfalls, and pumps. Even then, verify that the water flow is just at the right level for the Comet’s survival.

We can’t stress enough the significance of having a proper filtration system inside the tank. Forget about their small body size for a second. The Comet Goldfish produce enormous waste that can quickly sour the tank water when least expected.

Consequently, you should purchase a solid filter to control the ammonia levels and remove solid waste when necessary. For many aquarists, a simple canister or hand on the back filter is just enough to do that.

But the process changes if you keep your Comet fish in a backyard pond. Then, you won’t have better options other than powerful equipment that matches the pond’s capacity.

Common Diseases

Regardless of the habitat, your Comet Goldfish will be susceptible to parasitic infections like Ich and common bacterial infections.

Fortunately, Ich is only lethal if your fish are overwhelmed by increasing stress levels in the tank. Otherwise, you should have a good chance of saving the community with early intervention.

On the other hand, swim bladder disease is caused by constipation and bacteria and attacks the fish’s internal organs. In some cases, this condition never goes away. So, if the symptoms persist, you should seek a veterinary doctor’s advice straight away.

Finally, fin rot disease will target the beautiful fins that will either become discolored or fall off. But this should never worry you because simple over-the-counter antibiotics can quickly relieve its symptoms.

Whatever you do, never keep infected Comet Goldfish together with the rest of the community. It’s important to quarantine the disease-ridden species as soon as possible, as you focus on finding the right solution to save the situation.

What Do Comet Goldfish Eat?

Comet Goldfish are omnivorous species that will thrive with suitable food choices in the right quantities. Luckily, most of the food choices in the fishkeeping community already have all the nutrients Comet fish need to glow.

Their primary diet is top-quality dried foods from reliable sources. But in many cases, you should enhance their diet with the best alternatives such as live or frozen foods. These fish will happily feed on larvae, small insects, and bloodworms.

Also, Comet Goldfish enjoy plant-based varieties such as broccoli, lettuce, and peas. Bloating is a common issue with Comet Goldfish and is directly linked to overfeeding. To prevent that, you can restrict their diet to 2 or 3 meals a day within a 2-3 minute duration.

Behavior & Temperament

Comet Goldfish are social and peaceful fish that will never look for trouble inside the tank. They will quickly adapt to their new habitat and show their swimming prowess if healthy and comfortable.

For these Goldfish varieties, a successful day starts and ends with free-roaming inside the tank. The best part about their peaceful temperament is that they can coexist with various species without any trouble.

When keeping these Goldfish at home, your only concern will be the small fish. Comet Goldfish are not the best tank mates for smaller fish species because they will always see them as a nutritious snack.

Comet Goldfish Tank Mates

Comet goldfish are peaceful species that will never look for trouble inside the tank. However, the general assumption that these fish will live peacefully with most other species in the same space is never true. 

While their peaceful temperament makes them an excellent choice for many aquariums, a Comet Goldfish’s ideal tank mate should also withstand the cooler temperatures in the new habitat. And this is the most challenging part when selecting new tank mates.

Besides, Comet Goldfish have an enormous appetite, posing a significant challenge to the small, shy fish within the same territory.

With everything considered, here are some of the best tank mates you may want to try out with the Comet Goldfish:

As expected, you will want to ensure that the newly introduced tank mate is compatible with your Comet Goldfish. So, it’s important to monitor the new tank mate within the first few days to see how they interact with your Comet Goldfish.

You may have to reconsider your options if you notice the slightest form of aggression within the community.


Breeding Comet Goldfish is only possible with the right conditions, and smaller tanks shouldn’t even be an option. 

Outdoor ponds will give you the best chance of successful breeding at home, where the female Comet Goldfish will lay as many as 1000 eggs under the right conditions.

In many cases, Comet Goldfish breeding occurs in the spring season. So, you may be forced to recreate the warm conditions in the spring season to kick start the breeding process.

The general guidelines state that you should begin with cool waters for up to a month before increasing the temperature steadily to 70 degrees. You should consider spawning mops and artificial plants for the right breeding elements.

Don’t worry if the fish get chaotic at this point. It’s exactly what you should expect from the Comet Goldfish during the breeding season. 

Also, the spawning period requires careful supervision because Comet Goldfish are not as parental as you may perceive them to be.

Thus, they never hesitate to eat the fry if they have a chance. Typically, the eggs will take about one week to hatch, and the egg sacs will protect the fry until they learn how to swim.

The young fish will do well with baby brine shrimps and infusoria as their primary diet as they adapt to the new environment. 

Final Thoughts

Comet Goldfish care may not be straightforward, but it’s exciting for many reasons. It starts with maintaining the right tank water conditions while monitoring the fish’s general health and diet.

The journey will be challenging, but the unique bond you will create with your little Goldfish makes it worth it in the end. So, if you are up for the challenge, we can’t wait to hear about your amazing experience.

Hopefully, this guide will give you everything you need to keep a healthy Goldfish community at home!