"....Dropsy, I know you know, is very serious. If caught early,
sometimes the underlying infection can be treated before irreversible organ damage occurs.
I've never successfully treated dropsy myself, though I've only had two cases and that was very early in my fishkeeping experience and didn't know much about fish illness and disease.
I've read many many threads dealing with dropsy, and
most often things don't work out well. I've seen cases of improvement in the condition of the fish, restoring some quality of life and extending the life of the fish, only to have it return in a few months, but hopefully your little guy can be helped.
I've read a post that Lupin made in the case of a sick goldfish that I think would be a good protocol or treatment plan to try to help your little guy. Here is the suggestion Lupin made in this thread:
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http://www.aquariacentral.com/forums/showthread.php?p=2268393#post2268393
"...you do need to use metronidazole though which is the best way to treat dropsy. Epsom salt may work but not as effectively as sodium chloride does. Sodium chloride should be able to enhance osmoregulation and minimize fluid retention as much as possible. Dose 0.3% solution of salt and avoid ones containing ferrous cyanide or yellow prussiate.
1. Add a teaspoon per gallon first which is equivalent to 0.1%.
2. Repeat step 1 after 12 hours.
3. Repeat step 2. Same time interval.
Do not forget to redose salt per water volume changed when you make a water change.
What are your pH, KH and GH? You'd need to push the hardness levels by 150 or more. Use the API liquid drops to test accurately. Calcium chloride by Kent can be used to adjust the hardness levels temporarily to give your fish some relief from this issue as it also encourages proper osmoregulation."
Lupin
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Try to get some Metro and start treatment. I like to keep the water pristine, perfect, absolutely pure, so I do a water change, then dose, then in 24 hours do a water change and dose and keep this up until the full recommended course of antibiotic treatment has been completed.
I believe I would also add a little Epsom salts in addition to the table salt, following Lupin's guidelines as quoted above. Hopefully the table salt and epsom salt will help draw off excess fluid and, along with some Calcium, help keep electrolytes in balance.
If you don't have the test kits for hardness, or the Kent's Calcium Chloride, I would get a calcium tablet, a regular calcium suplemental tablet and break it in half and put about half of it in his water along with the meds and salts. You could use Tums to add calcium. If he's in a hospital tank of a gallon or less I would do half a Tums tab.
I don't remember the proportions on the Epsom salt, but I'd go with Lupin's recommendation on the NaCl (regular table salt), and maybe 1/4 teaspon of Epsom salts. (It may be that a bit more is better, but since I can't remember the exact amount I'd err on the side of caution.)
I hope if anyone has better ideas they will pitch in on this.
Chris, he may not make it. If his condition continues to worsen, euthanasia may be necessary. I would try to get some eugenol, (clove oil), to have on hand just in case.
I hope this helps. Please keep us posted.