NeoPlex is a broad spectrum antibiotic effective against most external infections of both marine and freshwater fish. Used as directed, NeoPlex will not discolor the water or damage the filter bed. It is well tolerated by invertebrates, although delicate species may be stressed. For use in freshwater or marine aquaria. NeoPlex is recommended for the treatment of certain diseases in marine and freshwater fish only. It IS NOT recommended for treating any style aquarium containing invertebrates, corals, crustaceans, or elasmobranchs (sharks and rays).