Buoyancy problems are signs, not a diagnosis
A goldfish may float, sink or roll sideways when it cannot control its position. Swim bladder problems are one explanation, but injury, body shape and other internal disease can produce similar signs.
Support the fish while seeking the cause
Keep water clean and well aerated. Reduce excessive current and protect the fish from abrasions without making the habitat too small. Check that it can access food; do not force-feed or attach a flotation device.
Why peas are not a universal treatment
A diet adjustment may help a feeding-related issue, but peas cannot treat infections or structural problems. Persistent loss of balance needs an aquatic veterinary examination; imaging may help identify the cause.
When to get professional help
Seek urgent help for severe breathing difficulty, bleeding, raised scales or inability to stay upright. Record exact water results and recent changes. A separate hospital aquarium must also be adequately filtered and aerated; an uncycled bowl can make the problem worse.
Frequently asked question
Should I medicate before testing the water?
Check water and oxygen promptly. Treatment should follow the likely cause; avoid mixing remedies without qualified guidance.
Sources and further reading
General husbandry and health references. Individual fish and local conditions vary.