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Passport
- Family
- Common Goldfish
- Grows to
- 30 cm (11.8")
- Lives
- 10–15 years
- TemperamentSuggested
- Peaceful
- Care
- Beginner
- Swims
- Everywhere
- Keep
- One is fine
- Water
- 10–23.9 °C (50–75 °F)
China
Care requirements
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On record for Common Goldfish: adult size, lifespan, minimum tank, temperature, ph, hardness, minimum group, diet, care level, swim level.
Not on record for Common Goldfish: tank length.
A figure that is not on record is left out rather than guessed. One marked Suggested comes from keeping knowledge rather than a page.
- Minimum tank 284 L / 75.0 US gal
- pH 6–8
- Hardness 5–19 dGH
- Diet omnivore
Care notes written from general aquarium knowledge, not from the cited sources.
About
Common goldfish are the most misunderstood animal in the hobby. They're sold as beginner pets for small bowls, and they are large, long-lived, cold-water pond fish that outgrow almost every tank they're put in.
A properly kept common goldfish reaches the size of a forearm and can live for decades. The stunted, short-lived fish most people encounter are stunted and short-lived because of how they were kept, not because that's the species.
They're also not tropical. They want cool water, they suffer in a heated tank, and they're happiest in an unheated tank or an outdoor pond — which is where a common goldfish really belongs.
Tank setup
Give your goldfish far more space than seems necessary, or give them a pond. This is the whole of goldfish keeping and everything else is detail.
Leave the heater out. They're a temperate fish and warmth shortens their lives, speeds their metabolism and stresses them.
Use sand or smooth gravel and keep decor smooth-edged. They root through the substrate constantly and they'll swallow small gravel.
Filter for far more waste than you'd expect. Goldfish are famously messy, and the filtration has to be sized for the fish rather than the water volume.
Cover the tank. They're strong and they splash.
Feeding
Goldfish are omnivores that graze more or less continuously and will eat until they're in trouble.
Feed a quality goldfish pellet as the staple, plus blanched vegetables — peas, spinach, courgette — and some protein like bloodworm or daphnia.
Soak dry food before feeding. Goldfish gulp air along with floating pellets and that contributes directly to the buoyancy problems the species is known for.
Avoid: overfeeding, which is the commonest mistake by a distance, and avoid cheap flake as a sole diet.
Filtration and flow
Over-filter substantially and change water often. Goldfish produce a lot of ammonia and they do it constantly.
Give them decent flow and good oxygenation. Cool water helps here, holding more oxygen than warm.
Vacuum the substrate regularly. They stir waste up and it settles back where they root.
With plants
Goldfish eat plants and uproot the rest. They graze soft growth and dig up anything rooted while foraging.
Tough species stand a chance — anubias and java fern attached to hardscape, sometimes vallisneria. Everything else becomes food.
Many keepers give up and use hardscape with artificial plants, which for this fish is a reasonable decision rather than a defeat.
Health
They're extremely hardy in cool clean water and prone to trouble in warm, small or dirty tanks.
Buoyancy trouble is common and it has more than one cause, so it is worth working through rather than guessing. Start with the water, since poor quality is behind a great deal of goldfish illness. Soaking dry food and feeding vegetables are sensible regardless. A fish that stays stuck at the surface or on the bottom, or that is clearly distressed, needs a vet who sees fish — some of these cases are structural and show up only on an x-ray.
Watch for ammonia. Goldfish tanks are under-filtered far more often than they're over-filtered, and burnt gills and red streaks in the fins are the result.
Breeding
They spawn readily in spring in a pond or a cool tank, triggered by rising temperature after a cold period.
Males develop small white tubercles on the gill covers and pectoral fins and chase the females hard, driving them into plants where the adhesive eggs are scattered.
The adults eat the eggs enthusiastically, so a spawning mop or dense plants lifted out afterwards is how you get any. Fry are easy to raise, take infusoria then baby brine shrimp, and start out a drab bronze — the gold colour arrives over months.
Tank mates
Avoid90
- Kribensis Common Goldfish grows to 30 cm against Kribensis at 8 cm, big enough to eat it.
- Least Killifish Common Goldfish grows to 30 cm against Least Killifish at 2 cm, big enough to eat it.
- Panda Garra Common Goldfish grows to 30 cm against Panda Garra at 9 cm, big enough to eat it.
- Scarlet Badis Common Goldfish grows to 30 cm against Scarlet Badis at 2 cm, big enough to eat it.
- Agassiz's Dwarf Cichlid Common Goldfish is not safe with Agassiz's Dwarf Cichlid: common goldfish and sth american cichlids - dwarf are a bad pairing.
Only with care16
- Chinese Algae Eater Chinese Algae Eater is aggressive and Common Goldfish is peaceful.
- Convict Cichlid Convict Cichlid is aggressive and Common Goldfish is peaceful.
- Jewel Cichlid Jewel Cichlid is aggressive and Common Goldfish is peaceful.
- Assassin Snail Common Goldfish is a risk to Assassin Snail: common goldfish and snails are a pairing to watch.
- Bladder Snail Common Goldfish is a risk to Bladder Snail: common goldfish and snails are a pairing to watch.