Comet goldfish care
Carassius auratus · Bred in the United States from common goldfish
Comets are single-tailed goldfish with a long, deeply forked tail, bred in the United States, fast and hardy enough for an outdoor pond.
- Tank size
- 75 US gal or larger
- Temperature
- 50 to 75 °F (10 to 24 °C)
- Group size
- 2 or more
- Temperament
- Peaceful
- Adult size
- 10 in (including the long tail)
- pH
- 7 to 8
- Hardness (GH)
- 6 to 18 dGH
- Lifespan
- 5 to 14 years
- Diet
- Omnivore
- Care level
- Easy
In a 75 gallon
48½ × 18½ × 21⅛ in outsideHow to keep comet goldfish
Comets are single-tailed goldfish with a long, deeply forked tail, bred in the United States, fast and hardy enough for an outdoor pond. Keep two or more in a pond or a 75 gallon or larger tank with strong filtration; they are too quick for fancy goldfish at feeding time.
Diet: Omnivore: sinking goldfish pellets, blanched peas and greens, frozen foods. Fish food types compared · how often to feed.
Where they swim: All levels.
Comet goldfish tank mates
Share the temperature and water, and neither side eats, nips or bullies the other. Check the full group in the stocking checker.
Common goldfish
8.7 in · 75+ gal · 50–75 °F
Shubunkin
12 in · 75+ gal · 50–75 °F
Dojo loach
10 in · 55+ gal · 55–77 °F
Denison barb
6 in · 55+ gal · 64–77 °F
Rubbernose pleco
5.7 in · 30+ gal · 68–77 °F
Blind cave tetra
4.7 in · 29+ gal · 68–77 °F
Paradise fish
3.5 in · 20+ gal · 61–79 °F
Reticulated hillstream loach
3 in · 20+ gal · 68–75 °F
Keep apart
Neon tetra: Adult comet goldfish eat fish under about 2 in; neon tetras grow to 1.6 in.
Cardinal tetra: Adult comet goldfish eat fish under about 2 in; cardinal tetras grow to 1.2 in.
Black neon tetra: Adult comet goldfish eat fish under about 2 in; black neon tetras grow to 1.5 in.
Green neon tetra: Adult comet goldfish eat fish under about 2 in; green neon tetras grow to 1 in.
Ember tetra: Adult comet goldfish eat fish under about 2 in; ember tetras grow to 1.2 in.
Glowlight tetra: Adult comet goldfish eat fish under about 2 in; glowlight tetras grow to 1.5 in.
What a comet goldfish tank needs
A tank of 75 US gallons or more (such as the 75 gallon) with a cover, and the equipment below. Comet goldfish are comfortable at room temperature, so a heater is optional in a normal home.
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Aqueon QuietFlow Canister Filter 300
Rated by the maker for 55–75 US gal, which covers a 75 gallon comet goldfish tank without being built for a far bigger one.
Marineland Penguin PRO 375
Rated by the maker for up to 75 US gal, which covers a 75 gallon comet goldfish tank without being built for a far bigger one.
API Freshwater Master Test Kit
Tests ammonia, nitrite, nitrate and pH, the readings that matter most before and after adding comet goldfish.
Seachem Prime 100 mL
Removes chlorine and chloramine from tap water at every water change.
Fluval Edge Thermometer
Shows the water temperature at a glance, but its display reads 64 to 86 °F, so it can’t show the bottom of the 50 to 75 °F comet goldfish range. Check it with a second thermometer that reads below 64 °F.
More choices, each with the reason it is in or out: Filters for a 75 gallon tank. We don’t list fish food: any good brand of the foods under Diet will do. Plan the whole tank's equipment →
Common comet goldfish problems
- They outgrow small tanks; a pond suits them best.
- Fancy goldfish lose food to them; keep comets with other single-tailed goldfish.
Test the water first whenever fish look unwell: see what your readings mean, then match the symptom. For disease, a vet who treats fish can diagnose it and advise treatment.
More to compare
Sources
Name and origin checked against Wikipedia: Carassius auratus. Adult size, temperature, pH, hardness, group size, lifespan and minimum tank size are common hobby guidance, not figures from that article. Ranges are the range the species tolerates; aim for the middle. Minimum tank sizes are for an adult group. Drawings are our own; photo credits follow.
Photo credits
Real photographs from Wikimedia Commons, resized and cropped to fit; each is used under the license named.
- Comet goldfish Michelle Jo (Humanfeather), CC BY 3.0, via Wikimedia Commons
- Common goldfish ぱたごん, CC BY-SA 3.0, via Wikimedia Commons
- Shubunkin Rodsan18 at English Wikipedia, CC BY 2.5, via Wikimedia Commons
- Dojo loach PrinceNimblesoft, CC0, via Wikimedia Commons
- Denison barb Anandarajkumar, CC BY-SA 3.0, via Wikimedia Commons
- Rubbernose pleco Frank Alvarez, CC BY 3.0, via Wikimedia Commons
- Blind cave tetra James St. John, CC BY 2.0, via Wikimedia Commons
- Paradise fish André Karwath; edited by Muhammad, CC BY-SA 2.5, via Wikimedia Commons
- Reticulated hillstream loach Spiketooth, CC BY-SA 3.0, via Wikimedia Commons
- Neon tetra Holger Krisp, CC BY 3.0, via Wikimedia Commons
- Cardinal tetra CHUCAO, CC BY-SA 3.0, via Wikimedia Commons
- Black neon tetra Debivort, CC BY-SA 3.0, via Wikimedia Commons
- Green neon tetra Sascha Biedermann, CC BY-SA 2.5, via Wikimedia Commons
- Ember tetra Klaus Rudloff, CC BY-SA 4.0, via Wikimedia Commons
- Glowlight tetra gonzalovalenzuela; cropped by Kyknos, CC BY 2.0, via Wikimedia Commons
- Fancy goldfish Benson Kua, CC BY-SA 2.0, via Wikimedia Commons
- Oranda Lawrencekhoo, CC BY-SA 4.0, via Wikimedia Commons
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