ParaGuard is a fish and filter safe parasite control product. Unlike highly toxic and difficult to use formalin based medication; ParaGuard contains no formaldehyde or methanol and will not alter pH. ParaGuard employs malachite green; and fish protective polymers that effectively and efficiently eradicates ich and other external parasites or fungal/bacterial/viral lesions. Great for quarantine tanks or whenever new fish are introduced. For marine and freshwater.