API Pond MelafixAPI Pond Melafix fish remedy acts as an all natural, antibacterial remedy for koi and goldfish diseases, including eye cloud, mouth fungus, fin & tail rot, damaged fins, ulcers, and open wounds. Use if you notice these symptoms among fish in your pond, or when adding new fish. API Pond Melafix fish remedy is safe for snails and other invertebrates, and will not harm aquatic plants, affect pH, or adversely affect your ponds natural biological filter.