Bubble eye goldfish
Carassius auratus
intermediate careOverview
The bubble eye goldfish (Carassius auratus) is among the most extreme and delicate of all fancies: a dorsal-less fish with two large, fluid-filled sacs beneath its eyes that wobble as it swims. It reaches 13–18 cm and lives 10–15 years. Those sacs are fragile, easily ruptured, and can impair its vision, so the bubble eye is a slow, vulnerable fish that demands a hazard-free tank and patient, experienced care.
Tank & water
Give one bubble eye 75 litres (20 gallons), plus about 40 litres per extra fish. Priorities:
- No heater, stable warmth: bubble eyes are cold-water fish that prefer a steady 18–23 °C as a sensitive fancy.
- Absolutely smooth décor: no sharp rocks, plastic plants or ornaments — anything can burst a sac.
- Gentle flow, guarded intakes: temper the external filter outflow and cover intakes with sponge so sacs aren’t sucked in.
Feeding
Bubble eyes are omnivores whose poor sight and slow pace make feeding difficult. Use a quality sinking goldfish food they can find on the bottom, give them plenty of time, and add blanched peas and soft vegetables. Sinking food also reduces the air-gulping that causes swim-bladder trouble in these dorsal-less fish. Feed small amounts once or twice a day and keep water pristine with regular maintenance.
Tankmates
Keep bubble eyes only with the slowest, gentlest fancy goldfish — celestials, ranchu, lionheads and other calm dorsal-less types. Never mix them with faster fancies, single-tailed goldfish like comets, or anything nippy, all of which will out-race them and risk damaging their sacs. They are not tropical community fish. A small group of equally delicate fancies is ideal — plan numbers with how many fish in an aquarium.
Because of everything above, the bubble eye is honestly a fish for a patient, experienced keeper rather than a first goldfish. If a sac does rupture it will often shrink and partly regrow, but the fish is then vulnerable to infection and needs pristine water while it heals. Kept alone or with equally gentle companions in a soft, hazard-free tank, though, a bubble eye is a genuinely charming and unusual animal that many keepers become devoted to.
Bubble eye goldfish — frequently asked questions
How big do bubble eye goldfish get?
Bubble eyes reach around 13–18 cm as small, dorsal-less fancies. They are still heavy-waste fish that need a large, gently filtered tank — see how big do goldfish get.
Do bubble eye goldfish need a heater?
No. Bubble eyes are cold-water fish, but as one of the most delicate fancies they prefer stable, slightly warmer water around 18–23 °C. In most homes no heater is needed — see do goldfish need a heater.
Can a bubble eye's sac pop?
Yes. The fluid-filled eye sacs are fragile and can burst on sharp décor or get caught in strong filter intakes. Remove all sharp objects, cover intakes, and keep flow gentle. A ruptured sac may heal but can become infected.
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