Description
The goldfish is the oldest aquarium fish there is: the Chinese have been selecting it for over a thousand years from a brown pond carp. And that is exactly why it is the most misunderstood. It is sold as a bowl fish, and it is a pond fish.
A healthy common goldfish passes 20 cm and lives fifteen years or more. It also produces a huge amount of waste: it eats constantly and digs through the substrate looking for more. In a few litres it does not grow "to fit the space", as is often repeated; it is poisoned and stunted.
Kept properly — a large tank, generous filtration and cool water — it is a long-lived, clever fish with personality that learns to recognise whoever feeds it. It simply needs what an animal of its size needs.
Behavior
Peaceful and sociable: better in a group of two or three than alone. It does not shoal tightly, but seeks the company of its own kind and spends the day rooting through the substrate.
It lives well with other goldfish and with coldwater species of similar size. In an aquarium, a goldfish-only tank is the sensible choice.
Avoid housing it with tropical fish, because the temperature ranges do not overlap and a goldfish demands a filtration load few can match; small fish such as white cloud minnows, or shrimp, which end up in its mouth as it grows; and fin nippers, especially with long-finned varieties.
With plants: it eats almost all of them. Only tough ones survive, such as anubias, ferns or large vallisneria.
Habitat
Carassius auratus comes from the slow waters of eastern China: ponds, canals, rice paddies and river backwaters with muddy bottoms and plenty of vegetation. It is a temperate fish that copes with cold winters and hot summers.
That tells you the essentials for the aquarium: it needs no heater, continuous tropical warmth does it harm and it appreciates a cooler winter. Outdoors, in a pond of some depth, it does better than in almost any aquarium.
There is no "original" wild population to copy: the domestic form has naturalised across half the world, and in Spain it is an invasive species that must never be released into rivers or ponds.
Details
🌊 Water parameters
🐠 Minimum tank size
Breeding
An egg scatterer. In spring, as the water warms, males chase females for hours and nudge their bellies until they release eggs among the plants. Mature males show breeding tubercles, small white dots on the gill covers and pectoral fins that are often mistaken for white spot.
Adults eat the spawn, so if you want fry the egg-laden plants must go into a separate container. One female lays thousands of eggs, and most fry of fancy varieties revert to the wild shape: breeding goldfish properly means selecting and culling, not just waiting.
Diet
Omnivorous and greedy, with a long gut built for a lot of plant matter.
- Staple: sinking pellets or goldfish gel food with a good share of plant content.
- Vegetables: blanched, peeled peas, spinach or courgette.
- Supplement: frozen daphnia or mosquito larvae, now and then.
Floating flake has a specific problem with this fish: feeding at the surface it swallows air, and in round-bodied varieties that ends in buoyancy trouble. Sink the food or soak it first.
And as always, less is more: a goldfish begs even when full.
What about your tank?
Enter your tank's values to see only the compatible species that fit them. Litres apply to fish.
Compatible fish
General guidance based on water parameters, behaviour and known exceptions; always review the individual animals' and aquarium's specific needs.
They share water: pH 6.5–7.5 and 24 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 6.5–7.5 and 22–24 °C.
They share water: pH 6.5–7.5 and 22–24 °C.
They share water: pH 6.5–7.5 and 22–24 °C.
They share water: pH 6.5–7.5 and 24 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 6.5–7 and 22–24 °C.
They share water: pH 6.5–8 and 24 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 6.5–8 and 22–24 °C.
They share water: pH 6.5–7.5 and 20–24 °C.
They share water: pH 6.5–7.5 and 18–24 °C.
They share water: pH 7–8 and 18–24 °C.
They share water: pH 6.5–8 and 22–24 °C.
They share water: pH 6.5–8 and 22–24 °C.
They share water: pH 6.5–7.5 and 22–24 °C.
They share water: pH 6.5–7.5 and 24 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 6.5–7.5 and 24 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 7.5–8 and 24 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 7.5–8 and 24 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 6.5–7 and 20–24 °C.
They share water: pH 6.5–7.2 and 22–24 °C.
They share water: pH 6.5–7.5 and 20–24 °C.
They share water: pH 6.5–8 and 15–22 °C.
They share water: pH 7–8 and 22–24 °C.
They share water: pH 6.5–7 and 22–24 °C.
They share water: pH 6.5–7.5 and 22–24 °C.
They share water: pH 6.5 and 24 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 6.5–7 and 23–24 °C.
They share water: pH 6.5–7.5 and 23–24 °C.
They share water: pH 6.5–7.5 and 20–24 °C.
They share water: pH 6.5–7.5 and 23–24 °C.
They share water: pH 6.5–7.5 and 22–24 °C.
They share water: pH 7–8 and 22–24 °C.
Compatible invertebrates
General guidance based on water parameters, behaviour and known exceptions; always review the individual animals' and aquarium's specific needs.
They share water: pH 7–8 and 20–24 °C.
They share water: pH 6.5 and 20–24 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 6.5–7.5 and 22–24 °C.
They share water: pH 7–8 and 18–24 °C.
They share water: pH 7.5–8 and 24 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 7–8 and 22–24 °C.
They share water: pH 7–8 and 22–24 °C.
They share water: pH 6.5–7.5 and 20–24 °C.
They share water: pH 6.5–6.8 and 20–24 °C.
They share water: pH 6.5–6.8 and 20–24 °C.
They share water: pH 6.5–7.5 and 18–24 °C.
They share water: pH 7–8 and 20–24 °C.
They share water: pH 6.5–7.5 and 18–24 °C.
They share water: pH 6.5–7.5 and 18–24 °C.
They share water: pH 6.5–7.5 and 18–24 °C.
They share water: pH 6.5–7.5 and 18–24 °C.
They share water: pH 6.5–7.5 and 18–24 °C.
They share water: pH 7–8 and 22–24 °C.
They share water: pH 6.5–8 and 15–24 °C.
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They share water: pH 7–8 and 15–24 °C.
Sources
- FishBaseFroese, R. and D. Pauly. Editors. 2026. FishBase. World Wide Web electronic publication.
Seriously Fish has no pages for pond fish. FishBase gives a thermal tolerance of 0 to 41 °C; the profile uses 15-24 °C, the comfortable aquarium range.
Plan your next aquarium
Is this fish right for you? Plan a suitable aquarium before setting it up.