Malachite Green Fish Disease Control - Kordon (DISCONTINUED)

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Kordon's Malachite Green will help control common parasites and protozoans like Ichthyophthinus, Costra, Chilodonella, Ambiphyra, Cryptocaryon, Epistylis, Oodinium and Trichodina. It is also very effective against certain fungal infections like Achlya and Saprolegnia that are commonly found on fishes and their eggs.


One size available - 4.0 oz. (118 mL) Treats up to 240 gallons

  • Treats external fungal infections, and parasites.
  • Treats fungal infections on fertile eggs.
  • Safe for freshwater and saltwater.

Note: This product is not Reef Safe


Suggested Directions & Procedures

Use 1 teaspoon (approximately 5 ml) per 10 gallons of water for most treatments. This produces a concentration of 0.05 ppm. At this concentration, 4 ounces of Malachite Green will treat 240 gallons of water.


Prevention or treatment of fungus on fish eggs:


Method 1 (Short Term Bath):

  • Change the carbon in the outside filter or add an outside filter with fresh carbon to the hatchery tank. Use a high-quality liquid phase activated carbon.
  • Start the filter.
  • Add 10 teaspoons of 0.038% Kordon Malachite Green per gallon of water. This produces 5 ppm activity of the drug.
  • Allow filter to run and allow it to remove the Malachite Green from the water for one hour. Note: If any color remains in the water after 1 hour, perform a partial water change of at least 25% change filter carbon and allow it to remove any additional Malachite Green.
  • Repeat treatment once a day prior to the hatching of the eggs. Discontinue after the eggs hatch.

Method 2 (Dip)

  • To a clean, non-metallic container, add 1 gallon of aged hatchery water, or water treated with NovAqua.
  • Add 5 fl. oz. of 0.038% Kordon Malachite Green (approximately 149 ml). This produces a concentration of 1500 ppm.
  • Agitate the solution with an airstone and adjust for a moderately strong flow of air.
  • Collect eggs in a net or grasp the object on which eggs are attached and dip them for not more than 10 seconds. Immediately replace the eggs into the original hatchery tank.

Note: This is a one-time treatment only. Do not repeat. The dip solution may be kept for future use. Keep container tightly capped when not in use.


Treatment for fungus on fishes

  • Transfer fishes to a separate quarantine tank, if possible.
  • Remove carbon, clean outside filter and return to use with clean mechanical filter media.
  • Calculate the actual volume of water to be treated, taking into consideration the displacement of water by sand and rock.
  • Add 1 teaspoon of Malachite Green per 10 gallons of water to the tank. This will produce a concentration of 0.05 ppm.
  • Make a partial water change of at least 25% every 24 hours and retreat. Superficial fungal infections will respond to a single treatment, while more advanced, deep-seated mycosis will require additional prolonged therapy. The disappearance of the strands (fungal hyphae) from the affected areas signals a successful treatment.
  • Upon completion of the treatment, return fishes to the original aquarium (if moved) and add Kordon's NovAqua or PolyAqua.


Treatment of ectoparasites:

The following procedure is applicable for control of ectoparasites in established aquaria, quarantine tanks, and outside ornamental ponds.

  • Transfer fish to a separate quarantine tank, if the treatment is to be used as a preventative measure. Note: while the fish may be treated in an established aquarium or moved to a quarantine tank, certain parasitic life cycles will require treatment in the aquarium or pond where the outbreak occurred, rather than the movement of those fishes which have been clearly affected.
  • Remove carbon and clean the filter. Replace filter media and return to use without the carbon.
  • If the treatment is being performed in an established aquarium or ornamental pond, it is recommended that a 25 to 50% water change be performed before treatment. Add Kordon's NovAqua when making water changes.
  • Calculate the actual volume of water to be treated, taking into consideration the displacement of water by sand and rock. (To calculate the aquarium's capacity measure its length, height and width in inches, multiply these dimensions together and divide the result by 232. Your answer will be the amount of water in gallons.)
  • Add 1 teaspoon of 0.038% Kordon Malachite Green per 10 gallons of water. This produces a concentration of 0.05 ppm. For treatment of Ichthyophthirius, the dosage can be increased to within a range of 0.10-0.15 ppm. However, this is not advisable for use when used with delicate fishes. Whenever possible, temporarily increase the water temperature during treatment with Malachite Green. An increase in temperature is beneficial since it speeds up the parasites' life cycle and decreases the required treatment period. The required total treatment period of any parasite must take into consideration the prevailing ambient water temperature and the parasites' life cycle.
  • Repeat the treatment with a partial water change of at least 25% daily. Add Kordon's NovAqua before replacing new water.
  • Upon completion of the treatment, return the fish to the original aquarium or pond (if transferred to a quarantine tank) and add Kordon's NovAqua or Fish Protector. If the treatment took place in the original aquarium or pond, change 40% of the water and replace the activated carbon in the filter.



  • Contains: Zinc free, chloride salt of Malachite Green.
  • Solution Concentration: 0.038% water solution
  • Stability: Indefinitely @ 0.038% water solution


Compatibility with other medications: Formalin or trichlorfon, NovAqua, and Fish Protector.


Cautions: Malachite Green is safe for use in closed systems that use biological filtration when concentrations do not exceed 0.10ppm.


Toxicity: Malachite Green varies with a number of factors including species of fish and its size, and less with prevailing water conditions. Malachite Green can be used at concentrations of 0.05-0.15 ppm. Used at 0.05 ppm, most species can be treated with little if any toxicity problems. However, care must be exercised when treating known sensitive fishes such as dwarf cichlids, barbs, tetras, gouramis, livebearers, catfish, loaches, mormyrids and scaleless fishes. Keep the fishes being treated under close observation and stop treatment, filter the water with activated carbon and perform a water change if any undue signs of stress are noted. AmQuel can be used to reduce treatment concentrations. Caution must always be exercised when using this product at dosages higher than 0.05 ppm. It is recommended that the literature be consulted in such cases for additional information on treatments.

Water conditions, in general, do not significantly influence the toxicity of the drug and therefore are not prime considerations for altering treatment procedures. When the drug is used in short-term exposures, Malachite Green may tend to be more toxic to some species in warm water than in cold water. Preliminary experiments have demonstrated that hardness or pH of the water has a negligible effect on increasing or decreasing the toxicity of the drug.

The effect on marine invertebrates is presently unclear and is not recommended. Until such information is available, use extreme caution if using Malachite Green in aquariums with invertebrates.

More Information
Product Name Malachite Green Fish Disease Control - Kordon (DISCONTINUED)
SKU 210588
Out of stock message DISCONTINUED
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