Protect your fish from long-lasting illness with API E.M. Erythromycin Freshwater Fish Powder Medication. This broad spectrum powder helps treat and control bacterial diseases including bacterial gill disease, body slime, furunculosis, hemorrhagic septicemia and mouth fungus. When used together with an ich, fungus or parasite treatment, this medication can protect your fish from catching another infection. Help your finned friend regain his strength, or prevent infections from spreading. The powder is safe for freshwater and saltwater tanks.