Comet Goldfish Pond Facts, Care, Lifespan & Breeding (Updated)

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Comet Goldfish Facts, Care, Lifespan & Breeding Guide for Ponds 2019

A sliver comet goldfish. Photo by Kurt Bauschardt. This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

The comet goldfish (Carassius auratus) is a variant of the common goldfish, distinguishable by its slightly smaller, thinner body and flowing, forked tail.

Like all other goldfish, they are related to carp but actually descended from wild goldfish hundreds of years ago. Specifically, studies have found that all current 300 domesticated goldfish breeds originated from a single domestication event that occurred within the incredibly biodiverse Yangtze River Basin in central China. Carp and goldfish belong to the same family, Cyprinidae, evolving from a common ancestor that they both branched off from into separate genera long ago. Comets specifically were bred in the United States somewhere around the late 1800’s.

Comets can be red, yellow, white, silver, orange, and just about anything in-between and any combination of these colors. They can be calico, but are unique in that their calico coloring isn’t the typical black and white, but rather red and white. They are happiest in ponds, as they are very active, playful fish that enjoy racing about and having plenty of space. Quite a hardy fish that is tolerant of both warm and cool waters, comets make a wonderful, easy to care for addition to any pond.


Comet Goldfish Maximum Lifespan & Size

A orange comet goldfish. Photo by Sheffield Tiger. This work is licensed under a Creative Commons Attribution 2.0 Generic License

If environmental conditions are right and comets are fed a nutritious diet, they can live up to 15 years. In an aquarium with less space, activity, and resources such as plants and other forms of stimulus, they will likely live closer to 5 years or less. They commonly reach up to a foot in length, give or take a few inches depending upon genetics, the size of the pond, and diet. In the first month of their life, they’ll increase their size by 50 to 100% each week, typically reaching full size by around 3 or 4 years of age.

After their first month, growth rates vary significantly, again depending on water quality, space, and diet. Some may grow half an inch per month, others an inch, and others maybe only a quarter of an inch.


Comet Goldfish Feeding & Nutrition – What’s the Best Food?

The diet of comet goldfish is the same as most other goldfish. Protein should make up between 35 and 40% of their diet and can consist of things like bloodworms, brine shrimp, soybean meal, and any insects that may be naturally present in your pond. During the first year or so of their life when they’re growing fairly quickly, increase protein to around 45%.

For the first month when growth is most rapid, protein can be as high as 60-70%. 10 to 20% of their diet should be composed of carbohydrates like shelled peas, unrefined cereals like plain Cheerios, raspberries, and citrus fruits. If fed too many carbohydrates, goldfish are known to develop liver degeneration. Lipids, or fats, should constitute 5-10% of their diet to ensure that they don’t suffer from stunted growth or deformities.

Feeding a high quality comet food will aid health, color and even growth.

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Due to their active nature, comets can be fed closer to the higher end of this range (lessening the amount again during winter, if needed, due to decreased activity during cold weather). Providing an adequate amount of both linolenic and linoleic acids, the two essential fatty acids needed by many common pond species, linseed oil is one of the best types of oil for fish. Fish oil is also acceptable.

Around 15% fiber, but no more, is best. Too much fiber inhibits the digestive system’s ability to properly absorb and utilize vitamins and minerals. Finally, ash should constitute approximately 6% of their diet


Comet Goldfish Pond Size & Pond Stocking

Although they can be kept in shallower aquariums, ponds need some depth so they’re able to stay warm in winter.

The pond depth should be a minimum of 3 feet, but increase this to 4 or more feet if you live in a region where water may freeze during the winter so that your fish can escape to deeper, warmer water. There should be roughly 50 to 100 gallons of water per comet goldfish to avoid overcrowding, ensure healthy water quality, and allow for plenty of space to swim about unhindered.


Comet Goldfish Winter, Hardiness & Water Quality

A orange comet goldfish. Photo by Sheffield Tiger. This work is licensed under a Creative Commons Attribution 2.0 Generic License

Comet goldfish are usually healthiest when the pH is between 7.2 to 7.6 and water temperature is within the range of 50 to 75° F (10-24° C), but can survive temps as low as 40° F (~ 4.5° C) and as high as 86° F (30° C), as well as pH levels as low as 6.5. As with just about any fish species, dissolved oxygen levels need to be kept at a minimum level of 5 ppm – lower than this and any fish, not just comets, will begin to have a host of health issues.

Try to keep oxygen levels between 6 and 7, though more certainly doesn’t hurt! Keep in mind that the more fish and other critters that you have in your pond, the more rapidly oxygen depletion will occur. Be sure to incorporate a filter to maintain water quality and reduce oxygen use via decomposition of organic matter, an aerator of some sort, and plants for natural filtration and oxygenation.

De-icers are important to keep breathing holes open in winter when ponds freeze.

During winter months, so long as your pond temperatures don’t dip below 50° F (10° C) during the winter, your comets should be just fine outside for the winter. If you have particularly bitter winters and are unable to keep your pond thawed, you can simply transfer your comets and any plants that can’t overwinter into an indoor tank. Always install a de-icer if you’re keeping fish outside to ensure they’re getting enough oxygen when the pond freezes over!


Comet Goldfish Tank Mates & Group Size

Comet goldfish are friendly fish and enjoy the company of other comets, as well as shubunkin and koi.

So long as you’re sticking to the 1 comet per minimum of 50 gallons of water rule, and keeping in mind the number and sizes of any other fish that you have, you can have as many comets as you’d like. They’re playful and social, and so do best with at least a few others of their own kind, as well as alongside koi carp, shubunkins, fancy goldish and other smaller pond fish.


How to Design & Plant Comet Goldfish Ponds 

Plants provide shelter for comet goldfish, as well as aid in the oxygenation and filtration of water.

A few plants that goldfish love for habitat (and sometimes as a snack) that are also excellent oxygenators include anacharis, hornwort, and water sprite. Comets do enjoy munching on plants, and may root around to get to their tender roots. You can place some plants, primarily emergent ones, on pond shelves that are too shallow for fish to swim to. Rocks too heavy to be moved by fish can also be place about the bases of plants, or you can place them in pots to protect the roots.

Some species, such as duckweed, are just too tasty to resist, though, so leaves will likely still get munched on. It’s a cheap plant and spreads very quickly easily, so this shouldn’t be an issue and will also provide your comets with a renewable source of nutrients while also keeping the plant’s population in check.


Common Comet Goldfish Diseases & Illnesses

A sliver spotted comet goldfish. Photo by Sheffield Tiger. This work is licensed under a Creative Commons Attribution 2.0 Generic License

Comets are somewhat prone to ich, or white spot disease, as well as swim bladder issues, fin rot, and fungal infections. These are all most often caused by poor water quality and/or improper nutrition. Be sure to perform 25% water changes weekly to maintain water quality, clean out any debris such as leaves daily, and conduct water quality tests at least once daily (at the same time each day to prevent any data bias from occurring). Keep pH, temperature, and dissolved oxygen levels within the parameters discussed above, and ensure that ammonia, nitrites, and nitrates are all kept to an absolute minimum.

Most fish purchased from aquariums and nurseries were raised on fish farms that are typically overstocked, prime habitats for illness and disease. As such, any time that you obtain a new fish, regardless of the species, be sure to quarantine the fish for a few days to observe for any health issues before placing it in your pond. This will greatly minimize the chances of spreading illness to your other fish.

Overall, keep your pond within comet’s preferred parameters, clean it and check water quality regularly, feed your comets a balanced diet, and they should live a long, healthy, happy, energetic life!


Comet Goldfish Breeding Behaviour & Requirements

Young comets. Photo by Jo Fothergill. This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

As with any fish, prompting spawning requires an environmental trigger. For comets, this consists of lowering the pond water temperature to approximately 58-60° F (14.5-15.5° C). The exact amount of time is contested, but two weeks to one month should work. If possible, during this same time decrease light to 6 to 8 hours per day (this may be difficult if your comets are in a pond – you can try shading the pond for part of the day if needed).

After this cool period, gradually raise the temperature by no more than 2° F (~1° C) per day until it reaches 70° F (21° C). Also increase light back up to 12 hours or more per day, if possible. This simulates winter passing and spring beginning, which is breeding season. Alternatively, you could simply let nature run its course and see if your comets will breed naturally once spring hits.

Spawning behavior is pretty easy to spot. Males will begin to chase females around and gently push against their bellies to stimulate them to release eggs. Females can release as many as 1,000 eggs, which will then attach to any plants and substrate in the pond. Males will swim over the eggs and fertilize them. Be sure to remove any adult and fingerling comets from the pond, as they’ve been known to eat the eggs. After about 2 days, the eggs should hatch, and after 2 more days the fry will be able to swim about on their own. You can cautiously reintroduce adult comets to the pond, but be aware that they may eat the small young. Another option is to place the eggs/babies in a quarantine tank or section off a portion of the pond for them.

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