Not reef-safe. Malachite green is lethal to shrimp, snails, crabs, and other invertebrates and can stain silicone and decor. Treat in a quarantine or hospital tank, or a fish-only system, and remove activated carbon while dosing. Kordon Malachite Green is a proven, zinc-free treatment for the most common external parasites and fungal infections of both freshwater and marine fish. It is a go-to medication for outbreaks of ich and velvet and for the cottony fungus that often follows an injury or stress. Reach for it whenever you need to clear an external parasite or fungus in a hospital tank. Browse the rest of our fish medications to round out your QT kit. What It Treats Used as directed, Kordon Malachite Green controls and helps prevent these common external parasites and fungal problems in freshwater and marine fish: Ich (white spot): freshwater Ichthyophthirius and marine Cryptocaryon Velvet: Oodinium Other protozoan parasites: Costia, Chilodonella, Trichodina, Epistylis, and Ambiphyra External fungus: cottony Saprolegnia on fish and on fish eggs, plus fungus associated with fin and tail rot How to Use Dose to the label. Follow the dosing chart on the bottle for your exact water volume; do not overdose. Pull the carbon. Remove activated carbon and turn off UV sterilizers and ozone during treatment, since they strip the medication out of the water. Treat in quarantine. A hospital or QT tank is ideal. Do not dose a display tank that holds invertebrates or corals. Repeat for ich. Ich and velvet have a multi-day life cycle, so repeat doses per the label, with a partial water change between treatments. Clear it after. Once treatment is finished, run fresh activated carbon to remove the residual dye and color from the water. Go gentle on sensitive fish. Use a reduced dose with scaleless and sensitive species, and watch the fish closely. Specifications Brand Kordon Active Ingredient Malachite green (zinc-free) Treats External protozoan parasites & fungus (ich, velvet, fungus, more) Water Type Freshwater & Saltwater fish Size 4 fl oz (118 mL) Reef Safe No, harms invertebrates and corals Use In Quarantine, hospital, or fish-only tank Recommended Pairings Kordon Methylene Blue for fungus, ammonia and nitrite detox, and a gentle dip option Seachem Cupramine for copper-based marine ich and velvet treatment in QT Fritz Maracyn if a secondary bacterial infection sets in Activated carbon to clear the medication once treatment is done Browse all medications and water care FAQ Can I dose this in my reef or planted display?No. Malachite green is harmful to invertebrates and corals, so use it in a quarantine or hospital tank, or a fish-only system without inverts. Does it treat marine ich?Yes, it controls marine ich (Cryptocaryon) as well as freshwater ich. Treating in a dedicated QT tank gives the best results. Will it stain my tank or hands?Malachite green is a strong dye and can stain silicone, decor, and clothing. Handle carefully and run carbon afterward to clear the color. Why remove the carbon?Activated carbon, UV, and ozone all pull the medication out of the water, so disable them during treatment and bring carbon back online once you are finished.
