Causes
Dropsy is fairly easy to diagnose non-specifically, however, it is much harder to diagnose the cause. The main cause is bacterial infection. The causative agent may be introduced through food or dirty water.
Dropsy is not very contagious; however, if a fish is diagnosed with dropsy, it is important to remove it from the aquarium because the infected fish will contaminate the separate water and end up dying. If there are multiple fish, treat the afflicted fish in a specially established "sick tank". Dropsy can spread from the ill fish, possibly causing stress among the other fish in the tank community. This extra stress may make the others vulnerable to dropsy or other forms of disease.
Treatment may consist of antibiotic targeting the causative agent. They work best in the very early stages of dropsy. A more hands-on approach is to raise the aquarium's temperature a few degrees - slightly higher than usual. Adding Epsom salt to the water helps to encourage the fish to expel unnecessary damaging fluids.
i thought dropsy are like, puffy scale?