i'm no doctor, but it sounds to me like that's more of a symptom than a disease in itself. if all of the fish in a setup are experiencing it, i would suspect that either it is some sort of internal parasite, or maybe water conditions. if it's a parasite, i'm sure there are available treatments. if it's a matter of water conditions try a good change.
additionally, you'll likely get answers from people more knowledgeable than myself if you posted this under the "food, water and health" section here rather than the marketplace.
best of luck in any event.