Paraguard is the only fish and filter safe aldehyde based 10 by weight parasite control product availabler suitable for freshwater and marine aquariumsr unlike highly toxic and difficult to use formalin based medications r paraguardtrade contains no formaldehyde or methanol and will not alter phr paraguardtrade employs a proprietary synergistic blend of aldehydes malachite green and fish protective polymers that effectively and efficiently eradicates many ectoparasites eg ich etc