Seachem ParaGuard 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, Seachem ParaGuard contains no formaldehyde or methanol and will not alter pH. Seachem ParaGuard 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.Ichthyophthirius (freshwater) & Cryptocaryon (saltwater)Looks like salt sprinkled on the fishs body and fins. Usually accompanied by twitching, flashing, and other signs of stress and irritation. Several parasites are grouped under this name, but the symptoms are almost identical. Ich is among the most common infections