Kordon Methylene Blue Disease Preventative – Safe for Freshwater & Saltwater Aquariums, Prevents Fungal Infections & Treats Parasites, Reduces Fish Stress, 4-Ounces

$7.49

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(as of Oct 07, 2025 09:47:40 UTC – Details)


Methylene blue is effective against superficial fungal infections of fishes. The drug may be used as an alternative to malachite green for the control of fungus when it is known that the fish to be treated are sensitive. Methylene blue is safe for use with fish eggs and fry for the prevention of fungal infections. As a secondary use, it is effective against some external protozoans, such as ich, chilodonella and costia.
Is Discontinued By Manufacturer ‏ : ‎ No
Product Dimensions ‏ : ‎ 2 x 2 x 5 inches; 0.32 ounces
Item model number ‏ : ‎ MODEL-37344
Department ‏ : ‎ Unisex-Adult
Date First Available ‏ : ‎ October 2, 2001
Manufacturer ‏ : ‎ KORDON LLC
ASIN ‏ : ‎ B00025646W
Best Sellers Rank: #5,628 in Pet Supplies (See Top 100 in Pet Supplies) #4 in Fish Medication & Health Supplies #30 in Aquarium Water Treatments
Customer Reviews: 4.7 4.7 out of 5 stars 3,564 ratings var dpAcrHasRegisteredArcLinkClickAction; P.when(‘A’, ‘ready’).execute(function(A) { if (dpAcrHasRegisteredArcLinkClickAction !== true) { dpAcrHasRegisteredArcLinkClickAction = true; A.declarative( ‘acrLink-click-metrics’, ‘click’, { “allowLinkDefault”: true }, function (event) { if (window.ue) { ue.count(“acrLinkClickCount”, (ue.count(“acrLinkClickCount”) || 0) + 1); } } ); } }); P.when(‘A’, ‘cf’).execute(function(A) { A.declarative(‘acrStarsLink-click-metrics’, ‘click’, { “allowLinkDefault” : true }, function(event){ if(window.ue) { ue.count(“acrStarsLinkWithPopoverClickCount”, (ue.count(“acrStarsLinkWithPopoverClickCount”) || 0) + 1); } }); });

Kordon methylene blue 4oz
Methylene blue is effective against superficial fungal infections of fishes
The drug may be used as an alternative to malachite green for the control of fungus

Customers say

Customers find the methylene blue treatment effective for treating sick fish and appreciate its quality, particularly noting it’s highly recommended for fish breeders. The product receives positive feedback for its value and versatility, with one customer mentioning it can be used as a general antiseptic. However, customers disagree on the product’s longevity, with some reporting their fish died while using it. Moreover, there are concerns about safety, as it’s lethal to live plants, and staining issues, with customers noting it stains everything it touches blue.

13 reviews for Kordon Methylene Blue Disease Preventative – Safe for Freshwater & Saltwater Aquariums, Prevents Fungal Infections & Treats Parasites, Reduces Fish Stress, 4-Ounces

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  1. Tina Wilson

    Fungus, not sure what’s going on. Fish need extra oxygen.
    I’ve been using methylene blue for a long time. I use it for fungus on my fish if I notice a little bit starting or if their coat starts getting a little slimy. I usually try this before I try anything else. Or if for some reason my nitrates or nitrite spike I’ll use this a little bit for some added oxygen if my fish start getting stressed out or are already stressed out. This has always worked very well for me. I’ve never had any fish stressed out about it. No headshaking ever like what happens when I add metronidazole or praziquantal or other meds.Methylene blue has also never hurt my pond plants. I don’t pour it directly in my pond. It’s always been in the hospital tank. I did recently use it when I bought some water hyacinth from a pond shop. I always bring them home and put them in a container with grow lights and heat to make sure that they don’t have a bunch of snails and dragonfly nymphs and whatever else there is on those things. Well, I ended up having a bunch of baby fry fish hatch from these plants. About a week later the little fry baby’s started turning white and dying. I wasn’t really sure what to due because I didn’t want to kill these plants that I just spent a couple hundred dollars for and I didn’t want to let the baby fish die. I added some methylene blue and some nitrofuranzone together with the baby fry and with the plants which also had snails, snail eggs, dragonfly nymphs on them and the white that I guess was fungus on these little baby fish I can’t really tell because they were so small. I did it once left it in there for two days and then the partial water change and I didn’t have any more baby fry fish die and my Hyacinth plants are still growing and still blooming. Some even flowered out purple flowers right away. So it didn’t hurt them at all. I was kind of disappointed about these plants and there had to have been something on them for these baby fish to get this but not only that the guy told me that they had goldfish in with the plants. I called And asked him after all these baby fries start hatching. I think something that people should think about, and I don’t know if people actually just buy plants and throw them in their ponds. I always did and I always ended up coming down with some kind of ailment around that time and I just thought it was a change in temperature, water parameters. But if the place where you buy the plants has goldfish or other fish in with them they have a fungus or bacterial infection and you bring those plants home and throw them in your pond you’re going to bring that stuff into your pond. So for now on I quarantine my plants.Back to the methylene blue. It’s definitely blue. I’ve never had it stain anything. I took pictures of what it looked like. It took pictures of my fingers after completely just dipping them in the stuff. And then the last picture I took was me washing my hands one time. It was almost completely off. Once I take a shower it’s completely gone. I’ve never had the methylene blue stain anything that I’ve ever had permanently. I think that having the methylene blue around in case you have something going on and you don’t know what it is is a fish lifesaver. You can at least be able to use it just in case you need to. It is better than not having anything at all. If I wouldn’t have had the methylene blue on hand along with the nitrfurazone at the time I’m pretty sure all the little fish would have been dead. Because that morning when I checked on them they had nothing white on them. Later that afternoon is when I started noticing it. About four of them died.So that’s my methylene blue story. I’m not sure how it would stain if you got it like on your rings or your jewelry or anything but it does eventually go away when I get it on my hands and stuff.

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  2. Tara Guest

    Great product
    Keeps my fish as healthy as can be. When I get them home everyone goes into a quarantine tank treated with this product befor going into my big tank!!! Would give 10 stars if I could

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  3. Mohammad Altaani

    Good deal
    Good quality, very strong and concenntrated. Easy to use. Very cheap. Safe for fish to have the fish for 5_ 10 minutes once a day for 5 days if the fish sick. Works very fast.

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  4. Nessie Binx

    Worked great
    Got it for my plecco that burned himself on a heater. Kept him in there for two weeks, slowly reducing the amount in the tank. It healed him great and he’s better than he was before. Can’t really complain besides it stains anything it touches, so don’t put it in your main tank lol

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  5. Brian V

    Effective, but a little leaky
    It appears to work rather quickly against Saprolegnia on Koi.Note: This bottle is a little leaky, and the stuff stains like heck. Use rubber gloves and keep the bottle in a bag in a bucket, and make sure it doesn’t come into contact with things you don’t want blue.

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  6. Maria C

    It really works to treat crayfish parasites.
    After some research I decided to buy this product to treat my blue cray fish that had parasites and some white stuff on his shell. Let me tell you after seven days he was free of parasites.

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  7. Arthur McDonald II, RN, APRN, MSN-FNP-C, MS-Ned

    Very Strong and Blue good medicine for your fish not you :}
    You get a lot for the price and it is of good quality, not diluted down.

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  8. Toto abukhalaf

    Good quality
    Good quality

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  9. Diana

    Muy bueno, con menos de una gota de cubren 50 litros

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  10. Conrad

    I have used this product to breed discus fish and it was very useful. I would recommend this item for sure

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  11. Alfonso

    Devo complimentarmi con il sito. Prodotto che ha soddisfatto le mie aspettative.

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  12. Client d’Amazon

    j’ai commandé ce produit pour mes poissons rouges qui étaient malades car a ma pharmacie il était beaucoup plus cher . Je pensais recevoir le produit rapidement il a mis plus de 2 moisdes poissons sont morts et la maladie prenant de l’ampleur J’ai du l’acheter a la pharmacieproduit très efficace qui a sauvé les autres poissonsdu coup me retrouve avec une bouteille entamée et une bouteille neuve si les problèmes recommencent je les auraient . PRODUIT EFFICACE

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  13. Sonney

    This product works really well. As someone who breeds fish and also keeps Axolotls I have used this multiple times and has always done its job. Used it for preventing fungus on eggs as well as treating fungus on Axolotls gills

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    Kordon Methylene Blue Disease Preventative – Safe for Freshwater & Saltwater Aquariums, Prevents Fungal Infections & Treats Parasites, Reduces Fish Stress, 4-Ounces
    Kordon Methylene Blue Disease Preventative – Safe for Freshwater & Saltwater Aquariums, Prevents Fungal Infections & Treats Parasites, Reduces Fish Stress, 4-Ounces

    $7.49

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