If you live in a country where medicated food and antibiotic water treatments are not available, this is an alternate treatment for dropsy, septicimia and other internal bacterial infections. Tri-sulfa has been successful in treating dropsy in two of my own fish and I am aware of two other cases that have also been successful.
There are several brands of tri-sulfa available, some are given as daily doses to the tank and others are given 3 days apart. The ingredients to look for in a tri-sulfer product are sulfadiazine, sulfadimidine, sulfamerazine.
These ingredients are monosodium salts so it is not necessary or advisable to also have high concentrations of regular salt in the tank, although I have salted to .1% without problems. Also it is not known how these monosodium salts react with epsom, although 2 cases that used TS also had epsom in the water without any obvious problems.
Tri-Sulfa appears to be very gentle on sick fish with no adverse reactions noted. It is not gentle however on bacteria and therefore should not be used in an established tank or it will send your cycle crashing.
Treatment should be in a hospital tank without filtration but an airstone is advisable for circulation. In all cases noted it was not necessary to heat the tank to achieve results so a plastic/rubber container would be ok. Check water parameters daily and do partial water change and redose medication if necessary. In my experience, using the treatment that is repeated after 3 days, it was not necessary to change any water until the third day. I believe this is possible because the TS so effectively kills all bacteria that there is none left to convert any waste into ammonia.
Recovery is usually obvious by the end of the treatment however it is advisable to keep the fish in the hospital tank with daily water changes for at least another week to allow it to convalesce.