Use antibacterial fin rot treatment. If your fish’s fin rot does not improve within a few days of cleaning and treating the tank, you may want to try antibacterial fin rot treatment. You can find this medication over the counter at your local pet store. Look for fin rot medication that is made for your type of fish, such as fin rot medication for a Betta fish or a goldfish. Follow the dosage directions on the label.[9][10]
These medications often contain antibiotics to kill off the fungal infection, such as erythromycin, minocycline, trimethoprim and sulfadimidine. Make sure the fin rot treatment does not contain any organic dyes, as they can be toxic to certain fish.
Popular types of fin rot treatment include Jungle Fungus Eliminator and Tetracycline. You can also use brands like Maracyn, Maracyn II, Waterlife- Myxazin, and MelaFix.[11]