Seachem Para Guard Parasite ControlSeachem ParaGuard is the only fish and filter safe aldehyde based (10% by weight) parasite control product available. Unlike highly toxic and difficult to use formalin based medications, Seachem ParaGuard contains no formaldehyde or methanol and will not alter pH. Parasite Control for marine or freshwater aquariums Contains no toxic methanol and will not alter pH Safe alternative to formalin Seachem ParaGuard employs a proprietary, synergistic blend