Seachem ParaGuard 500ml Bottles (3 Pack) 3 Pack of Seachem ParaGuard - 500ml Each Fish and filter safe parasite control The only fish and filter safe aldehyde based parasite control product available (for parasites on fish) Employs a proprietary, synergistic blend of aldehydes, malachite green, and fish protective polymers Effectively and efficiently eradicates many ectoparasites (ich, etc) and external fungal, bacterial, and viral lesions (fin rot)