Many people treat fish ulcers and dropsy in fish, with a variety of medicines, including antimicrobials. With the increasing concern of antimicrobial resistance (AMR) creating these life-saving drugs ineffective in humans and other animals, it is vital that you get a definite diagnosis prior to administering treatments for sick fish.
Bacterial diseases in fishes can be treated with certain antibiotics, but may be resistant to other antibiotics. Before treating your fish, always ask a veterinarian to take samples for laboratory testing so that a diagnosis can be obtained and the correct antibiotics provided (or treatment continued). Treatment may be prolonged and relapses can occur when treatment is stopped prematurely. Patients will need to be monitored after treatment ceases.
Please note that antibiotics can only treat against susceptible bacteria. It will have no effect on fish diseases caused by flukes and other fish parasites.
Be aware also, that there are risks to your own health, and to the fish , if used incorrectly. Always consult your fish veterinarian when using antibiotics to treat your aquarium or pond of fishes.