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. Directions: use 1 level measure (135 mg) to every 8 L (2 US gallons). Repeat every 7 days for up to 3 weeks or until symptoms disappear. Do not use UV, ozone, or chemical filtration during use. Remove with carbon before turning on UV.