Symptoms:
Dropsy is fairly easy to diagnose non-specifically, however it is much harder to diagnose the cause. The fish will appear very bloated, causing the scales to protrude much further than usual which gives the fish a rather distinct "pinecone" appearance.
The fish may also have sunken eyes, act lethargic, hang at the bottom or top of the aquarium, stop feeding and appear off colour.
Cure:
A few over the counter, commercial treatments have been developed for dropsy, however these are only sometimes successful in curing the fish. They work best in the very early stages of dropsy.
Antibiotics from your vet may also help, but once again they work best if given to the fish in the early stages. Antibiotics are in the majority of cases the best course of action.
A more hands on approach is to raise the aquariums temperature slightly ( a few degrees higher then usual) and add Epsom salts to the water at a rate of 20 mg/L.
Often when the diagnosis is made it is too late to save the fish. Symptoms can be moderate and when they do become severe the damage already done to the internal organs is too large for successful treatment. Thankfully dropsy is not very contagious, however if a fish dies of dropsy it is best to remove it from the aquarium as soon as possible.
Remember, water quality is always extremely important- so always check that first as it is often the cause of disease in aquarium fish. When treating sick fish, try to put the least amount of stress on them as possible, as stress will hinder the heeling process. Another thing is to remember is that generally, a healthy fish is a happy fish.