I normally don't even read the goldfish posts but advertising another forum caught the eye of one of our members so I came here. First thing, we do not allow advertising any other general purpose forums here. It is one of the rules if you read them, they are on every page and marked as general rules.
Next, back to the concern about swim bladder disease, it is not a disease in the way that the flu is a disease. Instead it is more a disease in the way that a broken arm is a disease. It is usually the result of a very specific injury that has cause the swim bladder, a part of the digestive system, to become enlarged and hold more gasses than it should. (A common cause is overfeeding when the fish is very young) I watched the surgery to correct this in a goldfish that could only swim upside down on the surface of his tank. No matter how hard he tried, he just could not right himself or swim away from the tank surface for long. He would go right back to the surface as soon as he stopped swimming downward.
The surgery was much like the surgery they do on overweight people to remove a part of their stomach so that they can begin to lose weight. In the case of the goldfish, they removed a part of his swim bladder so it could no longer fill with gasses and make him too buoyant. It worked to a degree but in the end, a few months later, he ended up dying anyway.
Something to be aware of before giving up on your fish is that swim bladder is often the words uttered by people seeing a fish having some kind of trouble swimming. It is quite often not the real problem. Misdiagnosis of swim bladder is quite common.
