Goldfish Floating Upside Down or Stuck at the Bottom: Swim Bladder Disorder, Symptoms and Treatment
Published by Planète Pets · managing editor: Clément Lacaille · how our guides are written
A goldfish floating belly-up, stuck at the bottom, or swimming sideways is almost always dealing with a swim bladder disorder — the gas-filled organ that lets it stay balanced in the water without effort. In the vast majority of cases, the cause is digestive: overfeeding, low-quality food, or eating too fast, which compresses the organ. Round-bodied varieties (telescope, lionhead, oranda) are far more prone to this than pond goldfish with a streamlined body, a link that echoes biologist R. W. Blake's review of fish swimming performance, published in 2004 (see the study): the further a body strays from an optimal streamlined shape, the more fragile its balance in the water becomes. Find our other pointers in the care and grooming section.
Contents · 5 sections
How do you recognise a swim bladder disorder?
The fish floats at the surface unable to dive back down, sinks to the bottom unable to rise, swims on its side or upside down, or struggles to keep its balance after every meal. Appetite often stays normal and the fish shows no other sign of illness: it's the swimming, not general behaviour, that should raise concern.
Why are round-bodied varieties more affected?
In orandas, lionheads or telescopes, generations of selective breeding have compressed internal organs into a short, rounded body, at the expense of the space left for the gut and the swim bladder. A slightly too generous meal is then enough to press these organs against each other, a phenomenon far rarer in pond goldfish with an elongated body, as covered in our guide goldfish tank size.
What treatment works at home, without medication?
Fast the fish for 24 to 48 hours to let the digestive system decompress, then offer a shelled, steamed pea with the skin removed: its fibre content gets the gut moving again without overloading it. Afterwards, resume feeding in small amounts twice a day rather than one large meal, to avoid a relapse, a principle covered in our guide overfeeding your fish.
When should you worry more?
If the disorder persists for more than a week despite fasting and peas, or if the fish loses its appetite and shows other signs (clamped fins, lethargy), the cause may be a bacterial infection or a congenital malformation rather than simple overeating. A specialist fish vet's opinion becomes worthwhile at that point.
Frequently asked questions
Does fasting hurt a goldfish?
No, a healthy adult goldfish easily tolerates 24 to 48 hours without food; it's even a recommended weekly practice to help prevent these disorders.
Does the pea trick work for all goldfish?
It mainly helps cases with a digestive origin. If the disorder isn't caused by constipation, the pea will have no effect and another cause needs to be found.
Can you prevent this disorder in round-bodied varieties?
Yes, by avoiding overfeeding, varying the diet, and offering smaller, more frequent portions rather than one large meal.
An accessory from our shop for this use: Hang-on isolation and breeding box for aquariums (€28.90) · the whole shop
This guide is part of Planète Pets’s Fishkeeping universe. Our advice is general in nature: for any health concern, your veterinarian remains the only reference.