A gentle antibiotic for fish that are already stressed.When a fish is weak from illness, a harsh antibiotic can push it over the edge.Seachem SulfaPlex is a safe, effective sulfathiazole treatment for many bacterial, fungal, and protozoan infections — especially the common bacterial and fungal diseases of freshwater fish. It's among the gentler antibiotics, great for already-stressed fish, easily removed with carbon, and won't impair nitrification.SulfaPlex is formulated with the science-driven chemistry Seachem has relied on since it was founded in 1979 in Madison, Georgia. As a company whose products are developed and manufactured in-house by chemists and backed by research, Seachem designed SulfaPlex to be gentle on already-stressed fish while remaining filter-safe — it won't impair nitrification in your biological filter — and easily removed with activated carbon after treatment. Remove invertebrates; turn off UV/ozone and remove carbon and Purigen. Dose 2–3 measures per 40 L (10 US gallons) every 72 hours, up to 3 weeks. Or bind to food with Focus for internal infections. Treat gently, even weak fish. Add to cart.Why Seachem SulfaPlex Among the gentler antibiotics: a safe, effective sulfathiazole treatment well suited to fish already weakened by illness. Filter-safe: won't impair nitrification in your biological filter during treatment. Easily removed with carbon: lift residual medication with activated carbon (MatrixCarbon) after treating. Versatile Seachem chemistry: a research-backed sulfathiazole formula that can be dosed in water or bound into food with Focus for internal infections. Best ForUse SulfaPlex in aquaria — especially freshwater — to treat bacterial and fungal infections including fin rot, bacterial hemorrhagic septicemia, mouth rot, fungus, and fur-coat syndrome, as well as protozoan infestations. Its gentleness makes it a strong choice when a fish is already stressed. Dose in water for external infections, or bind it to food with Focus for internal ones. Remove invertebrates before dosing in water.What It TreatsBacterial and fungal infections including fin rot, bacterial hemorrhagic septicemia, mouth rot, fungus, and fur-coat syndrome; also protozoan infestations.DirectionsDosing in water: Remove all invertebrates. Turn off UV and ozone filters and remove chemical filtration (MatrixCarbon, Purigen). Use 2–3 measures (included) per every 40 L (10 US gallons). Repeat every 72 hours for a maximum of 3 weeks.Dosing in food (feed daily until clear, up to 3 weeks): 1 scoop SulfaPlex + 1 scoop Focus + 1 tbsp food (pellets or frozen) + a few drops of water if using dry food. Use with GarlicGuard to enhance palatability.After treating: Remove with activated carbon (MatrixCarbon).Active IngredientsSulfathiazole (69%). Inactive ingredients: excipients (31%).Available Sizes5 g, 100 gFAQIs SulfaPlex safe for invertebrates? Remove all invertebrates before dosing in water. To treat internal infections while protecting invertebrates, bind SulfaPlex to food with Focus instead.How do I remove SulfaPlex after treatment? Run activated carbon (MatrixCarbon) in your filter once the course is complete to lift residual medication.Can I use SulfaPlex in food? Yes. Mix 1 scoop SulfaPlex + 1 scoop Focus + 1 tbsp food (with a few drops of water for dry food) and feed daily until clear, up to 3 weeks. GarlicGuard can improve palatability.