Bubble Eye Goldfish

Looks how to spot one

Scaled, dorsal-less twin-tailed goldfish with fluid-filled eye sacs

A small, smoothly curved goldfish with no dorsal fin and a double tail. Its upturned eyes each sit above a large, soft bubble of fluid that wobbles gently as it swims. The bubbles start forming about three months after hatching; some recent strains even carry four sacs.13

Personality what they are like

Very gentle and calm. A slow swimmer with a bobbing head, it does best away from boisterous fish, alongside other bubble eyes, celestials, telescopes and Black Moors.1

Daily activity how busy a day looks

Low. Prefers calm water with soft flow and plenty of unobstructed space.14

Grooming and care the hands-on bits

Needs a good filter, regular partial water changes with dechlorinated, temperature-matched water, and routine tests showing zero ammonia and nitrite. Choose smooth decor with no sharp edges, and fit a gentle filter with a covered intake to suit its soft eye sacs.45

Home where they are happiest

Keep in a filtered aquarium, not a bowl. Aqueon suggests at least 40 litres (10 US gallons) per adult fancy goldfish, while the RSPCA advises at least 60 litres per goldfish, with wider tanks giving more stable water. Fancy goldfish are comfortable at about 20-23 °C (Aqueon gives 68-74 °F), and the RSPCA notes goldfish in general live at 10-21 °C without a heater. A pH of roughly 6.0-8.4 is fine (FishBase gives 6.0-8.0, Aqueon 7.0-8.4).546

Food basics what goes in the bowl

Omnivore. Offer a goldfish flake, granule or sinking pellet once or twice a day, only as much as is eaten in two to three minutes, with frozen or live foods as occasional treats. Give it time to find food, as it is a slow, careful feeder.56

Company who they like around

Sociable; FishBase suggests goldfish in groups of five or more. Ideally kept in its own tank with other bubble eyes or similar slow fancies.61

The story where it all began

The bubble eye was developed in China from the toadhead, or hama-tou, a goldfish with upturned eyes and small bladder-like sacs. Breeders selected for ever larger sacs, and the toadhead is thought to be the ancestor of the celestial too.12

Recognised by the official bits

Taxonomy

Small, dorsal-less twin-tailed fancy goldfish with a large fluid-filled sac under each eye3

IUCN Red List

The parent species Carassius auratus is assessed as Least Concern6