Active ingredient: Aldehyde blend (10% by weight; no formaldehyde or methanol) + malachite green + fish-protective polymers
How to use (from the label): Dose: 5 mL per 40 L, repeated daily as long as fish show no stress. Course: Ich 14 days freshwater (up to 28 days saltwater); velvet 14-21 days; fin rot 7 days; flukes 14 days; quarantine 2 weeks. Prep: Remove all invertebrates and all chemical filtration (carbon, Purigen). Dip: 3 mL per 4 L for 1 hour
Careful: Remove invertebrates (not marketed as invert-safe; not for reef tanks). Sensitive and scaleless fish (eels, loaches, rays, sharks): start at 1/4-1/2 dose and build up. Plants: Seachem says generally safe but not guaranteed. Never combine with copper (Cupramine): aldehydes reduce copper to a more toxic form. Human: do not eat or drink, avoid eyes.
Rules: Malachite green is not FDA-approved for food fish in the US (unsafe new animal drug and unsafe food additive; carcinogenic concern). Seachem labels ParaGuard for ornamental fish only.
Never mix medicines unless the label says it is safe, and remove shrimp and snails unless the label says they are safe.
Examples you may see in shops: Seachem ParaGuard. Not endorsements. Always follow the label.
5 facts checked with sources