Dropsy pinecone effect koi pond fish

Dropsy is not a disease, it's a name for a fishes shape, and is an abnormal accumulation of fluid beneath the skin, or in one or more cavities of the body. The fish presents as generally swollen with scales standing out from the body Commonly called pine-cone effect).

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. They have mainly a mixed bacterial infection (aeromonas hydrophila and mycobacteriosis). Aeromonas (a genus of pathogenic rod-shaped gram-negative bacteria (schizomycetes) found in fresh and salt water, soil, and sewage) enter the body through intestines in the winter or spring and through ulcers, heron or parasites wounds.

Most fish with this problem survive for only 2-3 weeks but sometimes as many months. Often the belly becomes reddened shortly before death. 

Inside the fish the bacteria infect the kidneys and the liver. Failure of either one of these organs can course dropsy symptoms. Dropsy especially from liver or kidney damage can be so severe as to finally cause primary organ failure itself.

Symtoms

cessation of feeding
appear listless and lethargic
appear geberally off colour
sunken eyes
may hang at the top or bottom of the pond

Treatment

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" (Quarantine). 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.

Prognosis of fish dropsy is not good. By the time the fish has swollen up enough that the scales begin to raise, the internal damage may be too extensive to repair. Most cases of dropsy are fatal.

If the Dropsy is well advanced it is kindest to use fish anaesthesia. You must NEVER allow fish to die in a pond once dropsy has shown itself. This is because the bacteria will be released into the water.

Prevention

As with most fishe diseases, parasites and bacterial infections maintaining water quality is always extremely important.
It should always be checked first, because it is often the cause of disease in pond and aquarium fish. Frequent water changes can work to prevent the spread of disease by "watering down" the concentration of disease agents, and by reducing stress on the pond/tank occupants.

All pond and tanks need a 10-25% water change on a weekly basis. The best method of changing water is siphoning the water from the bottom, thus removing debris and fecal matter.
Always feed fish from reliable sources and use high quality food. Varying diet is also important.