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Common Goldfish

Carassius auratus

The *Carassius auratus*, or Common Goldfish, is absolutely the most iconic, abused, misunderstood and mistreated fish in the history of world aquariology. Aesthetically it retains the robust, elongated and muscular hydrodynamic shape of the wild carp from which it descends, but sports a solid, brilliant and stainless dark orange, red, yellow or metallic white livery. Despite being sold for a few cents as a disposable 'bowl fish', it is a formidable, intelligent and massive cyprinid that reaches 30 centimeters (12 inches) in length and can live happily for over 25 years. Its exceptional biological resistance is its condemnation: it tolerates conditions of pollution and asphyxiation that would instantly kill any other tropical fish, enduring silent agonies in tiny volumes. In reality, it is a tireless cold-water swimmer, destined exclusively for huge aquariums or outdoor ponds.

Taxonomy

Class:Actinopteri

Order:Cypriniformes

Family:Cyprinidae

Subfamily:Cyprininae

Genus:Carassius

Species:Carassius auratus

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Water Temperature

10 - 24 °C

pH Value

7 - 8

Water type

Freshwater

Tank level

All levels

Adult size

30 cm

Minimum tank volume

>= 150 L

Minimum group

>= 2

8 - 20 dGH

4 - 12 dKH

TDS

160 - 420 ppm

Conductivity

250 - 656 uS/cm

Species description

Geographical Origin and Habitat: Native to East Asia (China). The wild form inhabited slow-moving rivers, lakes, muddy ponds, and ditches. Domestic forms, the result of over 1000 years of captive breeding (Song dynasty), do not exist in the wild but have been introduced worldwide, becoming cosmopolitan.

Taxonomy and Morphology: Cyprinid with a torpedo base shape (robust and hydrodynamic) or compact egg shape ("Fancy"). The common goldfish easily reaches 30 cm (12 inches) in length. It lacks true maxillary teeth but has powerful pharyngeal teeth in its throat to crush food, and lacks a true stomach, presenting a long, continuous intestinal tract.

Social Behavior: Gregarious fish, sociable and a tireless explorer. It spends most of its time rooting the bottom, sucking and spitting the substrate. Must be kept in groups (at least 3-5 specimens). Totally harmless to its own kind, it may accidentally swallow smaller fish simply out of gluttony.

Coloration and Sexual Dimorphism: Brilliant colorations ranging from red, deep orange, yellow, white, or calico. Sexual dimorphism is evident only during the breeding season or in mature fish: males develop "breeding tubercles" (small white, rough dots) on their gill covers and the first ray of the pectoral fins.

Care, breeding and tankmates

Aquarium Setup: Let's dispel the myth: they CANNOT live in glass bowls or small tanks. A common specimen requires AT LEAST 150 liters (40 gallons), with large open swimming spaces. Substrate must strictly be fine sand (which it can spit easily) or very large stones, to avoid lethal choking caused by sucking angular gravel. Prefers smooth wood and tough plants (Anubias).

Diet and Feeding: Voracious omnivore with a strong vegetarian base requirement. The lack of a stomach requires small, frequent meals (twice a day). Provide sinking pellets (never floating, which cause air swallowing) and heavily supplement with blanched vegetables (peas, zucchini, spinach) to prevent fatal constipation and swim bladder inflammation.

Water Quality: Temperate water fish, not tropical. Ideal temperatures 15.0-24.0 °C (can tolerate ice in winter ponds). pH 7.0 to 8.4 and medium hardness (GH 8.0-20.0). They produce an immense amount of waste: requiring frequent partial water changes (at least 30% weekly) and oversized industrial filters to handle the massive ammonia load.

Compatibility and Cohabitation: Total incompatibility with tropical fish (tropicals die of cold or goldfish die from accelerated metabolism at 26°C). Do not pair fast "Comet" or "Common" variants with slow and clumsy "Fancy" variants (Oranda, Black Moor), as the former would steal all their food leading to starvation. Excellent pond companions are Koi Carp.

Aquarium Breeding: Prolific free-spawner. In spring, as temperatures rise, the male chases the female, nudging her abdomen to stimulate the release of thousands of adhesive eggs among vegetation. There is no parental care; parents immediately devour the eggs if they do not fall into inaccessible areas or if they are not separated.

Risks and Diseases: The greatest risk is ammonia poisoning in insufficient volumes, causing fin necrosis and gill burns. Extremely prone to swim bladder inflammation (buoyancy issues) due to intestinal constipation from incorrect dry feeding. Extremely vulnerable to muscle atrophy in small spaces.

Geographic Origin and Distribution

Native to East Asia (China). The wild form inhabited slow-moving rivers, lakes, muddy ponds, and ditches. Domestic forms, the result of over 1000 years of captive breeding (Song dynasty), do not exist in the wild but have been introduced worldwide, becoming cosmopolitan.

Origin

Selective breeding and cultivarsEurope, Mediterranean, and West AsiaEast AsiaCosmopolitan or introduced

Fish profile

Temperament: Peaceful
Diet: Omnivore
Life expectancy: 10-15 years
Sex ratio: School
Feeding frequency: Twice daily
Bioload: High
Flow: Weak
Jump risk: No
Reproduction: Oviparous
Compatibility & tankmates: Species only
Tank level: All levels

FishBase

Window to the official scientific data of the species

Data synced on: 06/15/2026

Scientific Parameters & Models

Trophic level: 2 ± 0 se
Resilience: Medium (1.4 - 4.4 years)
Generation time: 6.7 years
Phylogenetic uniqueness (PD50): 0.5156
Bayesian Length-Weight: a = 0.01259, b = 3.04

Image gallery

Licensed images linked to the species or, when marked, to the closest representative taxon.

Related species

Recommendations grouped by close relatives, companion choices, and similar care.

Variants and close relatives

Same atlas type, nearby scientific identity, genus, or family.

Comet Goldfish

Carassius auratus var. Comet

Species description

Care, breeding and tankmates

Geographic Origin and Distribution

Origin

Fish profile

Scientific Parameters & Models

Image gallery

Related species

Variants and close relatives

Comet Goldfish

Rosy Bitterling

Eurasian Minnow

Rummy-nose Rasbora

Emerald dwarf rasbora

Belica

Rosy Barb

Denison Barb / Roseline Shark

White Cloud Mountain Minnow

Garra Rufa (Doctor Fish)

Java Barb

Odessa Barb

Zebrafish

Gold Barb

Purple Rose Danio

Yoma Danio

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