Some are benign, some are malignant. If found in your stock or fry, it is best to destroy the fish. Some fish with air bladder problems lie on the bottom of the tank and make efforts to rise, only to relax to the bottom again. Others may float and be unable to swim downward. This is because of inflamed organs that reduce the size of the air bladder, or inflammation of the air bladder.
Scales appear to stand on end, and fish looks bloated.
This may be signs of an intestinal infection. Fish cannot swim below the surface without exertion, and many stay in upright position. Bacteria invades portions of the fish's body, and then collects in areas. Collects behind the eyes and pops them forward. Fish quickly dies.