Paraguardtm 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, paraguardtm contains no formaldehyde or methanol and will not alter ph. Paraguardtm employs a proprietary, synergistic blend of aldehydes, malachite green and fish protective polymers that effectively and efficiently eradicates many ectoparasites on fish (e. g. Ich, etc.) and external fungal/bacterial/viral lesions (e. g. fin rot).