API® Furan-2 powder Contains two furan compounds to combat a wide variety of gram-positive & gram-negative bacterial diseases, including bacterial gill disease, open red sores (Aeromonas spp.), body slime & eye cloud, black molly disease (Flavobacterium columnaris) and fin & tail rot. For use in both freshwater and saltwater aquariums. This medication will harm the biological filter. Note: This medication will cause a slight discoloration of water which can be removed with activated carbon.