well epsom salt won't actually treat swim bladder disease. Swim bladder disorders are very common among round-bodied
Goldfish because of their specific anatomy. The internal organs of a round bodied
Goldfish are actually somewhat "squished" towards the front of their abdomen. You will often hear people suggesting that you soak the fish food before feeding it to
Goldfish and that is because
Goldfish commonly gulp food at the surface. When the food is gulped dry, it expands inside the fish and can easily become lodged in the "squished" digestive tract of the fish.
Goldfish are also different anatomically because they have a pneumosystic duct which is a passage way from the swim bladder to the esophagus. The pneumosystic duct is used to help regulate the air in the swim bladder and if there is a blackage in the digestive tract then it can cause a swim bladder problem and lessen the fish's ability to regulate bouyancy. I know this is off topic but this is why epsom salt has been recommended for swim bladder disorders. Epsom salt is a natural laxative and so therefore it can help swim bladder disorder if it is caused by a blockage in the digestive tract. I used to always give our round bodied
Goldfish unshelled peas too since the source of fiber also helps to make sure their digestive tracts are clear.
So to answer your questions TR:
1)in my experience I see swim bladder disorders more commonly in round bodied
Goldfish and that is most likely due to their anatomy and eating habits as I pointed out earlier. Most fish do not have digestion problems like that though so epsom salts probably wouldn't do much. Generally swim bladder disease is bacterial or parasitic and it is difficult, if not impossible to tell which it is. I would say most commonly it is bacterial in which the bacteria causes the walls of the swim bladder to thicken and harden a little and not allow air to pass through the membrane and regulate bouyancy. In that case medicine is your best bet.
2) I have no clue what the approprate rate is, haha. I always just eyeball everything like i'm some professional chef

I would say the same dosage you would use for normal salt though, about a tablespoon per 5 gallons I think.