Malachite Green
  • ShukriShukri March 2011
    Posts: 4,881
    Since I have not contributed to the Forum in a while, so here goes........ There are friends in the koi keeping hobby that have asked me to start this (i.e. koi medication), so this is my first attempt.

    Scientific name is Malachite Green and the color is kaki green.
    Formula: [C6H5C(C6H4N(CH3)2)2]Cl and is not related to Malachite Cu2(CO3)(OH)2 (found in nature)
    It is a chloride salt.

    Potential Health Effects
    Eye: May cause severe eye irritation. This product contains a cationic dye. Similar dyes have caused permanent injury to the cornea and conjunctiva in documented exposure cases with human or rabbit eyes.
    Skin: May cause skin irritation. May be harmful if absorbed through the skin.
    Ingestion: Harmful if swallowed. May cause gastrointestinal irritation with nausea, vomiting and diarrhea.
    Inhalation: Dust is irritating to the respiratory tract. May be harmful if inhaled.
    Chronic: Possible risk of harm to the unborn child.

    Malachite green (MG) is a synthetic dye used to colour silk, wool, jute, leather, cotton and paper. The name comes from the similarity of colour of malachite green to the mineral, malachite.

    Malachite green has traditionally been used to treat fungal infections on fish and their eggs.

    It is not usually used to treat bacterial diseases. But the bacteria Flavobacterium columnare is sensitive to this dye.
    It is a potent chemical dye and is often used as a 1% solution (typically use 1g of powder dissolved in 100ml of distilled water) and then dapped directly onto the infected area of the fish with a cotton bud daily until the infection is healed. Or a bath is made and the fish dipped into it for a time.

    This dye's effectiveness is reduced by light, therefore during treatment turn the tank lights off.
    Note: This chemical is harmful to humans!

    Various ornamental fish treatments use this dye. It will probably be banned from the ornamental fish hobby in the near future due to concerns of its risk to humans.

    Malachite Green and Formalin are two of the key chemicals for treating fish disease and have been used for many years against a range of parasites. They can be used together or separately as anti-parasite treatments against as Gyrodactylus (skin flukes), Dactylogyrus (gill flukes), Ichthyobodo (Costia), Trichodina , Chilodonella and Ichthyophthirius (white spot).

    Malachite green also has powerful anti-fungal properties and is used against Saprolegnia (fungus) either when present on fish or to as a treatment to protect fish eggs from infection.

    On a personal basis, I have used a dosage of 1-2 grams per metric ton of water to combat against fungal and bacteria infections. I do not believed that the MG will wipeout the bacteria colony in the filter chambers nor the main pond. During treatment, I normally switch off the UV light. I have also use MG as a topical applicant, and it worked fine.
    I normally let the MG to be soaked in the pond for 5-7 days.

    Malachite Green & Formalin should not be used (not recommended) when the salt level in the pond is higher than .1%.

    Other koi Sifus, please add your knowledge and experience to this discussion.

    In Koianswers Forum, no one individual is above the rest. This is the Forum for the Koi Community.
    Post edited by Shukri at 2011-03-13 08:48:25 pm
  • ikankoikauikankoikau March 2011
    Posts: 1,053
    Bro Shukri,
    Thanks for starting this thread. For the dosage of the MG, I only use 0.2 to max of 0.7 gram per ton(1000L). Dare not try above 0.7g per ton. Can any bro confirm the correct dosage?

    Using MG together with Formalin can combat against some parasites, bacteria and fungus at one go.
  • PH8PH8 March 2011
    Posts: 683
    Not an authority by any stretch of imagination, but here's my 2c on MALACHITE GREEN.

    1. Usage - dosage to pond if many fish in the pond seem to be having fungus infections (especially cloudy white on the head or body). Can also be applied topically on the infected parts.

    2. Pond Dosage Rate - typically 0.2ppm - 0.8ppm, depending on how serious the problem is. This translates to 2-8g per 10 tons of water. Personally, I find that using 2g/10tons is usually good enough to clear fungal infections, but do give it several days to clear. A repeat dose is usually unnecessary unless the fungus is still there a week after the first dose.

    3. How to Dose - After weighing the correct dosage in crystal form, mix it well into a pail of water. Personally, I pour the crystals into an empty litre water bottle, add water, screw on the cap and shake hard for several minutes to get the solution well dissolved. It is then poured very slowly (I actually do it over about 30 minutes to reduce the shock factor) into the pump chamber from where it gets evenly distributed into the pond. Better to dose in the evening/night and remember to switch off the UV lights. Since MG is possibly carcinogenic, it is advisable to wear gloves during the mixing/treatment process and exercise due care.

    4. Effect on the Water - the water will turn dark green, but still clear (not milky). This colouration normally lasts for less than 24 hours when I dose 2g/10tons.

    5. Effect on the Koi - As with any other form of medication, the koi will react to the addition of MG, but their reaction is much less than for salt or PP since MG does not result in sharply lower TDO levels. The koi don't gather in a bunch at the surface but swim around looking relatively relaxed.

    6. Feeding - I normally restart feeding the day after the treatment, after the water clears of the colouration.

    7. Effect on Filter - I suspect (but am not sure) that heavy doses (say 0.5ppm or more) on 2 or more consecutive days (which I have personally never done) MIGHT kill off a lot of the good bacteria in our filter. In such an event, I would put in a precautionary dose of bacterial starter on the day that I restart feeding, and also salt to 0.15% to buffer against nitrite spikes. This is not necessary if just a single 0.2ppm MG dose is done.

    8. Water Changes - No special requirements, I just continue with my normal routine of 5-10% daily water changes.

    Important note - Many senior hobbyists prefer to use Methylene Blue to treat fungal outbreaks, since it is not carcinogenic like Malachite Green. The only reason why I personally use MG is that a koi brother gave me 2kg of it and it takes forever to finish using it, even after passing some to other koi brothers!
    Post edited by PH8 at 2011-03-14 03:04:02 am
  • mosquitomosquito May 2011
    Posts: 26
    Hi Bros,

    Would it be lethal still even if only half a dose of MG is applied to a pond of 0.5% salt? Thanks in advance.
    Post edited by mosquito at 2011-05-11 08:37:25 pm
  • ShukriShukri May 2011
    Posts: 4,881
    Bro Mosquito, to answer your question.......I have not read anywhere saying that MG can't go with salt. But I have not tried it before. Having 0.5% salt is stressful enough to the kois, and adding MG will definitely add more 2 cents worth.

    If you are curious enough, why don't you do the R&D...... :)
    In Koianswers Forum, no one individual is above the rest. This is the Forum for the Koi Community.
  • mosquitomosquito May 2011
    Posts: 26
    Bro Shukri,

    Thanks for the input. I guess I'll bring down the salt first before I make any stupid move. In this case curiosity could end up killing all the kois and not the cat #:-s

    Post edited by mosquito at 2011-05-11 11:04:20 pm
  • heng84heng84 May 2011
    Posts: 77
    I've tried before 0.4% salt with mg was ok for me but better be safe
  • herbieherbie August 2012
    Posts: 2
    hi there

    i have a 10,000 gallon pond and want to treat with malachite green crystals how many grams will i need to use for this??

  • ShukriShukri August 2012
    Posts: 4,881
    Bro Herbie,
    Please be correct on the dosage OK! Only 0.2 grams per 1 metric ton of water. Make sure you use an electronic digital weighing equipment.

    Is the 10,000 gallons an US gallon or British gallon? I US gallon equals 3.8 liters and 1 British gallon equals 4.5 liters.

    And also, please also check from a second source that what I am saying here is correct, and my assumption here is correct i.e. with regards to the gallon conversion that is........
    In Koianswers Forum, no one individual is above the rest. This is the Forum for the Koi Community.
  • herbieherbie August 2012
    Posts: 2
    its british gallons mate i have been told 13 g is what i need for a 10,000 gallon pond
  • ShukriShukri August 2012
    Posts: 4,881
    Based on my calculations..........10,000 British gallons equals to 45,000 liters so 45 metric ton. 45 X 0.2 equals 9 grams.......

    Based on my calculation is 9 grams needed.
    In Koianswers Forum, no one individual is above the rest. This is the Forum for the Koi Community.
  • robrob April 2013
    Posts: 1
    I have a 8000 us gal pond and was going to treat for white stuff on fins of fish. We it kill my bog filter?
  • ashfaqashfaq January 2014
    Posts: 799
    Brothers, bought MG from singapore in liquid farm.
    What will be the dosage for liquid form?
    Ashfaq from India-Chennai
  • spencertanspencertan January 2014
    Posts: 227
    Hey bro Ashfaq.
    I believe the dosage for the liquid form depends on the concentration of the liquid.
    As such, there may be instructions on the bottle of the liquid. Perhaps you can follow the instructions on the bottle if any?
  • ashfaqashfaq January 2014
    Posts: 799
    While importing, i have been suggested to remove the label.
    Hence didnt read the instructions
    Ashfaq from India-Chennai

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