What should I do about my gold fish that has swimming bladder disease?

First, do a 30% water change. Then, crush peas into the aquarium at feeding time. You can just use canned peas from the store for this, and all of your fish will benefit. What happens is when the fish eat at the surface, they swallow air. This throws off their buoyancy, and the peas will expel the gas. Do this every other day for at least 2 weeks. If these don't seem to have any effect, you might have to start treating the fish with antibiotics as it could be a bacterial infection causing this.