Aquarium Pharmaceuticals Pond Care Melafix Naturally Treats Bacterial Infections On Koi, And Other Pond Fish. Pond Care Melafix uses a powerful antibacterial found in Tea Trees. Open wounds, ulcers, tail & fin rot, and damaged fins are rapidly repaired using this extract. All-natural, won't harm plants, & safe to use in all ponds. Works great when introducing new fish as well. Use as directed. 16 Oz. treats up to 4,800 Gallons.