ParaGuardâ„¢ is the only fish and filter safe aldehyde based (10% by weight) parasite control product available (for parasites on fish). Unlike highly toxic and difficult to use formalin based medications, ParaGuardâ„¢ contains no formaldehyde or methanol and will not alter pH. ParaGuardâ„¢ employs a proprietary, synergistic blend of aldehydes, malachite green, and fish protective polymers that effectively and efficiently eradicates many ectoparasites (e.g. ich, etc.) and external fungal/bacterial/viral lesions (e.g., fin rot). It is particularly useful in hospital and receiving tanks for new fish and whenever new fish are introduced to a community tank.