It is never easy to carry out euthanasia on any creature, but it is the most prudent thing to do in the case of Dropsey, as there is no cure for it.
"Horton"

Dropsy is a SYMPTOM of other problem(s) with the fish. Dropsy can be due to problems with the environment (water quality, temperature shock, alkalinity), parasites, bacteria or virus.
The symptoms are:
1. scales lifting (pine coning) and/or
2. swelling without scales lifting (ascites) and/or
3. both eyes bulging (exothalmia)
Many people say that dropsy isnt curable. The earlier that dropsy is caught treated, the better the prognosis. Here are pictures of a VERY dropsied fish before and after using Jo Ann Burke's treatment method for a fish with dropsy caused by bacteria. Click HERE or on the name DROPSY.

DIAGNOSIS
Are both eyes bulging? Fish with only a single bulging eye is most likely mechanical damage. The best treatment for this is clean water and a little salt.

Check the water parameters, ammonia, nitrites, nitrates, pH, alkalinity and temperature. Was there an ammonia or nitrite spike? Are nitrates high? Was the temperature of the water matched during the last water change? Was the alkalinity of the water changed suddenly?

Do Jo Ann's 3 point physical. Are there any indications of fried gills, bacterial infection, parasites? Have the fish been showing any other behaviors of degraded water quality, parasites or bacteria?

Do a scrape and look for parasites if you have a microscope.

If the temperature in the tank or pond has dropped suddenly, prognosis is very good for treatment.

TREATMENT: If parasites are likely, treat for them first for 3 days increasing the temperature to 86oF as fast as possible. Do NOT use salt, use epsom salts and use extremely good aeration.
SOLUTION: Check the temperature of the water when doing water changes.
Water quality must be maintained.
Feed antibiotic food in fall when temperatures start to decline in the pond.
Use a tank heater to prevent temperature drops when air conditioners are used, or when tank temperatures fluctuate more than 2-3 degrees per day.

Pop-eye is sometimes caused by Edwardsiella ichtalori (info supplied by the Goldfish Guru). It is carried by frogs and turtles, especially if you are in the south. Feed Romet B, but better is
inject chloramphenicol if in the south or amakacin if in the north (amakacin seems to be pH dependent, works best in alkaline water).

A number of us have found that keeping the heat up to 84-86oF of for 2 weeks minimum, keeping oxygen levels high and feeding with antibiotic food like Romet B has brought most of them around. We don't know for how long.

Little to no salt, and 1/8 teaspoon of epsom salts per 5 gallon water. The temp alone kills most strains of Aeromonas. Feeding erythromycin laced food (soak dry food) or romet B will kill the second suspected bacteria, mycobacterium.

The salt thing is counterintuitive. It is rational to think the salts would "draw" the fluid out, but actually, the fish is having a hard time getting rid of salts, which is why it is blowing up.

The epsom salts, on the other hand, will not pass through the walls of the gut or gills, and is supposed to "draw out toxins". It definitely pulls water out of the surrounding tissue into the gut when used as a laxative.

No one is sure if this is a cure (when done for at least 2 weeks). But I have not had a relapse so far (7 months I think) if the fish make it through dropsy.

Dropsy and ascites are different. In both cases fish blows up, but when the scales stand out, this is more normally called dropsy or pineconing. This is more treatable. Ascites, when the fish blows up but the scales are flat usually goes along with no ammonia which points to kidney damage. If the fish has ascites and is producing ammonia, maybe this too is curable.

In discussion with Jo Ann, of the 5 causes of dropsy (parasitic, bacterial, viral, temperature shock, toxic water), Jo Ann says caused by bacteria can be cured by high heat because aeromonas is killed by high heat.

I am not so sure that heat is only responsible for killing bacteria. Bob Gray talked about dropsied fish that were only fine in hot water, the minute the temp was reduced, they dropsied again. It didnt seem that the bacteria returned, rather it seems to point to some physiological defect where the fish could not regulate water intake/output at lower temps. In humans, some people get heat stroke and once they have had it once, they are always susceptible. It is tied in with electrolyte imbalance as ingesting gatorade AND taking cold showers reverses the condition. Without taking electrolytes and bringing the temp down, the body temp just keeps rising until coma and death. So electrolyte regulation is tied in to heat somehow. And electrolyte imbalance is tied into edema, like in congestive heart failure, where fluid is lost into the tissues across the capillary bed and cannot be brought back in.

GF whole metabolism is tied into temperature. Dropsy is the loss of electrolyte/fluid control. In GF, it seems the imbalance and swelling works opposite of humans. A quick drop in temp can trigger dropsy. And moving fish from soft to hard water can cause dropsy. So I think that bringing the temp up may treat dropsy by another mechanism, as in the case of Bob's fish.

Reason why the heat method doesnt work for some fish
1: PRIMARY INFECTION IS NOT TREATED OR IS AGGRAVATED
Bacteria are rarely the primary infecting agent. Fish are normally quite well protected against bacteria by their slime coat. Parasites large enough to get thru the slime coat disrupt the slime coat and allow bacteria to enter. If GF with active parasites are moved into hot water, this causes an explosion of parasites (who's reproduction is tied to temp). So the parasites have to be treated first. If the fish isnt badly dropsied, a quickly salt dip and a day or two treatment at lower temps with medication is called for. If the fish is badly dropsied, there may be no time for medication, then a quickly salt dip (30 seconds) that kills some of the parasites outright, and reduces the number of them by stripping the slime coat must be used. The fish must be put into fresh water to prevent reinfestation from without. Moving them to fresh heated water every day keeps them from reinfestation. Again, running the temp up with an active parasite load can kill the fish.

Reason why the heat method doesnt work for some fish
2. THERE IS TOO MUCH SALT IN THE WATER
NaCl salt has to be removed from the system and magnesium epsom salts added, but only 1/8 teaspoon per 5 gallons. More is not necessarily better. Softened water may contain quite a bit of sodium ions without being obvious by taste.

Reason why the heat method doesnt work for some fish
3. TOXIC WATER
Fish are moved to hospital tank to protect tank mates, but also in case the dropsy is due to poor water conditions in that tank. When fish doesnt respond to fresh hot water, this does not rule out toxic water as there may be some basic underlying problem with the water, not enough natural electrolytes, alkalinity, carbonate hardness/buffer or something, right out of the tap. When fish do respond, it is time to investigate what may be toxic in the tank they came from, like carbon leaching crud back into the system, or gravel leaching dyes or organic crud or toxic gases.

Reason why the heat method doesnt work for some fish
4. THE TEMP IS RAISED SLOWLY
The temp is run up fast, not slowly. It is rapid temp DROPS that can shock the fish. Running the temp up is not the same as taking a fish from cold water and dropping them into hot water. Bacteria replicate in as little as 20 minutes, and adapt incredibly fast to "marginal" conditions by natural selection. Inching the temp up slowly may select for those bacteria that can function/reproduce at higher temps. I dont know that this will in fact happen, but using marginal conditions for selecting resistance is done all the time in the lab.

Reason why the heat method doesnt work for some fish
5. TREATMENTS WITH TOXIC MEDICATIONS
No treatment, not even antibiotics kill every single last bacteria. The fish MUST have a functional immune system to regain health by developing immunity that does stop bacteria and viruses. If the fish is so stressed by conditions or toxic water, or by the addition of medications, they will not have functional immune system. All medications are toxic to one degree or another. Medications that are USELESS not only do nothing to help the fish, it may prevent the fish from recovering. Jo Ann has basically tested most of them on the market. She has found the meds that work, the ones that dont and the ones that are simply too toxic to be useful. Now, she hasnt tested them all, and, Jo Ann points out that meds toxicity and usefulness IS different in different kinds of water, soft vs hard for example. IN GENERAL, antibiotics in the water dont work. Injected is best, followed by antibiotic food. As an addition, the immune system "turns over" very fast.

Reason why the heat method doesnt work for some fish
6. STARVATION
To build immunity fish need protein and energy. They need GOOD food with antibiotics in it. Fasting them is not helpful. As long as fish are pooping, they should be force fed if they are not eating. A fish has enough reserves for a couple to 3 days, after that, get out the syringe. If the fish wont eat the romet B but eat a little chopped shrimp can be fooled by soaking romet in shrimp oil or other fish oil.

Reason why the heat method doesnt work for some fish
7. NOT KEEPING THE FISH AT THE CORRECT TEMP OR NOT KEEPING THEM THERE LONG ENOUGH
Get a good thermometer. With aeration, the temp can be set to 86oF to make sure the water stays warm. New fresh water must be kept above the minimum of 84oF. It takes a minimum of 4 days for dropsy to begin to resolve, to see the scales starting to return to normal. And it takes a month for "the treatment to "hold" in most fish when the temp is finally lowered. The fish doesnt have to be moved bucket to bucket for the whole month. The bucket to bucket method keeps the fish ahead of anything they might be shedding and preventing reinfestation. A few days after the scales are down, the fish can be moved into a tank with a filter (make sure the filter is clean) as long as the heat is continued. When the treatment is done, it needs to be lowered slowly, like 2oF per day until it is at the temp the tank of the other fish are kept at.

Reason why the heat method doesnt work for some fish
8. THE PRIMARY CAUSE IS UNKNOWN OR UNTREATABLE

IN POND FISH
First you need to treat the parasites if the fish is out of a pond. If the slime coat is still thick, a quick salt dip will strip it off, then PP or Quick Cure for 3 days. Do this in a bucket, moving the fish to fresh water every day or more depending on ammonia buildup. You have to heat the water up to 84-86oF and add 1/8 teaspoon per 5 gallons. An injection of antibiotics is good, but if no access, feed romet B antibiotic food or soak something dry in oxolinic acid. It takes a minimum of 2 weeks (and more like 1 month of moving the fish every day and heat to stop the dropsy.

Don't quit the heat if the scales go down. Don't stop the epsom. It takes this long to get the toxins or whatever out of their system. Stop sooner, and they relapse easily. Dropsy can also be caused by quick drops in temps, but only in susceptible fish.