Fancy goldfish always swimming upside down

[Flowersinthewateringcan]

DS18 has a cold water fish tank with 3 fancy goldfish.

One of the fish, which he purchased last year, seems to be suffering with a swim bladder issue. He is constantly upside down on the surface of the water, it really struggles swimming normally or moving to the bottom of the tank. It does eat still.

DS has had the water checked, keeps the tank clean and has lots of fresh plants in the tank etc. He has tried swim bladder treatments but the poor thing isn’t getting better, it really can not be much fun for it living like this.

Any suggestions what we can do to help?

[OldTinHat]

I would phone your local aquatic centre, explain what's happening. They're normally good with advice about this kind of thing.