Although there is a specific condition known as dropsy, which is probably incurable, a swollen body with raised scales can actually be caused by many other things. Therefore you might get lucky and the fish might respond to a treatment, but it can be very difficult to know what the underlying condition actually is - and it can just be old age.
When a freshwater fish becomes ill or stressed, its internal regulation can break down causing it to absorb water through the process of osmosis, because dissolved salts in the water are more dilute than its body fluids. Freshwater fish have to regulate this by passing large quantities of dilute urine, and if the balance is upset, the fish can retain water and may bloat from the osmotic pressure.
By contrast, salt water has a higher concentration of salts than a fish, so for marine fish the pressure is in the opposite direction - the fish constantly loses water so has to drink a lot and produces only small amounts of concentrated urine. When the balance breaks down here, instead of bloating the fish will shrivel and appear 'pinched'. Marine keepers will be familiar with this - the opposite of pine-coning but essentially caused by the same thing(s).
Sorry, not much help regarding your particular issue, but understanding that most cases of dropsy are probably not dropsy at all might help in identifying an underlying issue - or perhaps that there is no issue and that sadly the fishes time is simply up.
When a freshwater fish becomes ill or stressed, its internal regulation can break down causing it to absorb water through the process of osmosis, because dissolved salts in the water are more dilute than its body fluids. Freshwater fish have to regulate this by passing large quantities of dilute urine, and if the balance is upset, the fish can retain water and may bloat from the osmotic pressure.
By contrast, salt water has a higher concentration of salts than a fish, so for marine fish the pressure is in the opposite direction - the fish constantly loses water so has to drink a lot and produces only small amounts of concentrated urine. When the balance breaks down here, instead of bloating the fish will shrivel and appear 'pinched'. Marine keepers will be familiar with this - the opposite of pine-coning but essentially caused by the same thing(s).
Sorry, not much help regarding your particular issue, but understanding that most cases of dropsy are probably not dropsy at all might help in identifying an underlying issue - or perhaps that there is no issue and that sadly the fishes time is simply up.
