The Aquarium Pharmaceuticals PondCare Melafix is an antibacterial remedy for the treatment of koi and goldfish diseases including eye cloud, mouth fungus and fin & tail rot. All-natural antibacterial remedy rapidly repairs damaged fins, ulcers and open wounds. Use when adding new fish to the pond. Safe for snails and other invertebrates. Will not harm aquatic plants, affect the pH or adversely affect the biological filter. Treats 19,000 gallons.