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Malachite and formol or salt treatment ?

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  • Malachite and formol or salt treatment ?

    Coming back home, I had the bad surprise to see some ulcer on a tail of a kohaku male and on a kikokuryu male. I don't have any other ulcer on other parts of both fishes. I have the intention to put all my koï in a bath of green malachite and formol tomorow and then repeat the treatment a few days.
    I am a little affraid af the stress to manupulate everybody, so would you think that a salt treatment in the main pond could be an other solution ?
    If you think to a better treatment, please tell me about it .
    Thank you and have a nice week end.
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  • #2

    Have you checked your water for ammonia and ph problems this looks like is it caused by bad water. The red stricks in the fins are a sign of stress and I think you might want to do a water change. Better yet a total pond clean out.


    • #3


      I thought too that I had stress problem, but I could not find the reason.You might be right, Koifishgirl, with the water quality because even if all my analysis are good, I cover the pond during the night with a floting cover to spare the heating system. So even if my filter go on, the air exchange mihgt not be sufficient and that could be the reason of the stress.
      I thank you, Koifishgirl, and tonight no cover for anybody..


      • #4

        Marco: I'd recommend that you go to and search the threads for suggestions. (Click on "community" at the top of the screen and follow along the steps to the health forum.) After you have reviewed, you may have a specific question.

        In the meantime, your proposed treatment may rid your koi of parasites which caused the ulcers, but the parasites are likely still in your pond. And, depending on the parasite, your treatment might not be the right one. Without a microscope, nobody will know for sure. However, more often than not, flukes are involved. Malachite green & formalin will treat those, but salt likely will do you no good. Personally, if parasites are implicated, I think it best to treat the whole pond.

        The ulcers are symptoms of a bacterial infection, likely resulting from bacteria invading the punctures made by parasites. Your proposed treatment will not address the bacteria. Antibiotics are needed. Depending on the nature and seriousness of the infection, it might be possible to treat with antibiotic/sulfa drugs added to a hospital tank, or you might obtain benefit from medicated foods, but those who really know about ulcer infections will tell you that injection of antibiotics is the way to go. If at all possible, warm the water. Never under estimate the power of a koi's natural defenses. To get it's microbe defenses into high gear requires warm water.

        And, as suggested above, focus on your water quality as well.

        Good luck! Let us know how well/poorly it goes.


        • #5

          Marco: I've been thinking about what I posted and the pics you posted. Several years ago I acquired a small Showa that had been shipped from Japan to a dealer in the U.S., who immediately took it on a 14 hour road trip to a show, where I bought it. That poor fish had been bounced around in Japan, put through all the rough handling of air cargo, bounced along the highways and put in a sales vat. Along the way, it had multiple potassium permanganate dosings to rid it of parasites. Within 2 weeks of arriving at my house, it had fin rot much like your pics show. But, the fish had a healthy appetite and no symptoms of parasites. The idea of injecting antibiotics was not anything I was prepared for, and the fish had not cost as much as the antibiotics would have cost. I isolated the koi in a hospital tank with a dose of 400mg erythromycin per 10 gallons (U.S.) of water dissolved in the water, with a dose of 200mg per 10 gals. being repeated every 24 hours for 5 days. No food during that time. A 50% water change was performed daily using water stored overnight with the identical temperature. After the 5 days, the koi went into a small, shallow pond which had temperatures ranging in the mid-70sF. At that point the bloody streaks in the fins had improved quite a bit, but were not gone. I fed it medicated food only. It had a couple of goldfish as company, and the pond was shaded from direct sun all but a few hours of the day, with shady cover. After another 7-10 days, the fins were clear. After another month, the fins had re-grown. There were no lasting visible defects.

          The point of the story is that I jumped to an assumption that you likely had parasites. Maybe not. Stress from environmental factors may have weakened the fish so they became susceptible to an infection. Search for the possible causes of stress to your fish. I suspect flukes are there, but maybe it is something else that triggered the infection.

          Second, I wanted you to know that it really is possible to save them without injecting antibiotics. Often koikeepers quickly go for injections, forgetting that not everyone has access to the antibiotics, nor the money for it, nor the knowledge of what to do. So, do your best for the koi. We are still wishing you luck.


          • #6

            I may be wrong but I am sure that the other members in the forum will correct me if I am but I am thinking that if you cover your pond every night the bad stuff is not being evaporated in the air. I have heard that this will cause water problems. Maybe you dont need to cover every nite.

            Guys what is it that need to evaporate into the air?


            • #7

              I believe the problem exists with water quality. water change and some salt
              may arrest the problem. I'm against treating for something without knowing ahead what it is your dealing with. If the covering of the pond at night is not allowing it to breath, that may be a BIG problem right there. I would give way on the temp abit to allow for it to degass properly.
              Dick Benbow


              • #8

                Yes Dick I think your right with that one . I can see where covering a pond all night could cause a water problem. I would think you could smell the stuff when you lifted the cover. Red fins like that are a sure sign of water quality problems.

                And thanks for telling me what it was that I could not remember, sometimes I just get these brain farts. Kind of funny the older I get the more it happens


                • #9

                  itll only gets worse if the waters bad. if you fix the water it should fix itself.
                  i agree salt bath would help, water change defintaely.

                  antibiotic injections last- your problems not bad enough for that.
                  people shouldnt jump at those things anyway.

                  malachite also a bit nasty, carcinogenic. take care with it. better still try avoid it too. sorry to anyone that sells the stuff but its not nice stuff.
                  for thsat problem you dont need the big guns..

                  formalin, if you must - 25 ppm if being safe 40 ppm if your sure of what your doing.
                  they can handle as much as 60ppm but you i think you can fix it with salt bath and water change on main pond.
                  that stuff is bad too.

                  i dont think there is a safety data shhet for salt or water changes and that will fix your problem.

                  sometimes i wonder if carcinogenic substances are bad to us, then how is it for the fish in the long run?

                  ive recently sold some baby fish to a uni student that is checking a herbicide that we likely put into the water ways- shes not seeing if it kills them outright but looking at the effects of the fishs endocrine system.


                  • #10

                    Thank you to everybody for the goos advices you gave me.

                    My water analysis seems normal.

                    I took my microscope home this afternoon to search some flukes like Mike was sujesting and I found them...
                    Maybe they are not the main responsable of my problem, but anyway I will treat the pond with Supaverm.
                    I will heat my pond with a higher temperature and put my flotting cover away and wait a few days to see how everything is going on. If the problem doesn't take a good evolution, I will make an antibiotic injection (Nuflor) to the two hill kois and salt the pond.

                    Anyway I will let you know in a few weeks the result of the treatment and send some picture again, and once again thank you.



                    • #11

                      You have a scope! Great!!

                      Confirming one problem is a good first step. There may be something more, but take one at a time. Also, remember that the medications are all stressors themselves. So, take your time before deciding to use another. A few people report having problems when they use salt with Supaverm, but most experience no problems. I suspect overdosing with Supaverm combined with salt may be involved in the bad experiences, but do not know. (Most people over-estimate their pond volume if they do not meter a fill-up.) Although most have no problems, I would wait a couple of days after using Supaverm before adding salt. Do not use anything else with Supaverm until the 10 day treatment period is concluded and you have done a water change. Hopefully, nothing more is needed.

                      Good luck!


                      • #12

                        So, here are the last news of my problem.

                        I treat the flukes with supaverm but the sickness continue to contaminate others koï. I phone to my Koi dealer and he said that he also had an oïdium problem, the best solution for him was to treat the pond with formalin and malachite (three treatment , one each two days) . Of course my filtre has to be re feed with bactogen , but all my koi are now in perfect conditions and the littles white ulcer desepear from all of them without lmeaving any injury.
                        I don't post any pict because I don't want to stress them more, but once again thank to all people who gaves me good advices


                        • #13

                          Their response sounds like it could have been the dreaded salt-tolerant Costia. Can you tell us what the concentration of formalin and malachite was? Are these fish from Japan?
                          -steve hopkins


                          • #14

                            hey steve, i dont know what he used but our doses for formalin are 25ppm for light dose, 40ppm for a good dose, and sixty if your careful and really wanna nail something. im interested in his dose rate too.


                            • #15

                              Hei Bekko,

                              I use a mixture made with one litre of Formaline (a solution with 35 % formaldehyde) and 3.3 grames of green malachite.
                              In my pond I put 15 ml of the mixture for 1000 litre (my pond has about 12000 litre and I put 180 ml each two days and this, 3 times).
                              I had no sign of toxicity on the fish, but a put massive oxygen in the water from the day before the first treatment until two days after the last one.
                              I increase the temperature to 20 degree with a heater system and they had only a little food only the days without treatment and only once a day, just to see if the apetite was stil there.
                              That must be a concentration of 15 ppm of formaline and 0.05 ppm of green malachite, but I leave the week end to control ..

                              I bought a kin kikokuryu a few month ago, coming from Japan and he was one of the first to be hill, so it could be a costia problem . But I never detect them on microscope and I try a few time without results. Could be my foult that I did not see them, but I use the microscope every day in my work and I normaly know how to find such protozoaire.

                              I think I will never know for sure what was my problem, and that is a little frustration, but what a pleasure to see them getting better after only two days treatment.
                              So have a nice week end and enjoy your koi


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