Kordon Methylene Blue General Disease Prevention Aquarium Treatment, 4-oz bottle

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About This Item

Details

  • Liquid medicated formula is effective against fungus on fish, and for the prevention of fungal growth on fish eggs.
  • Also treats some external protozoans like Ich, Chilodonella and Costia, and provides protection to prevent infections.
  • Works in both freshwater and saltwater aquariums and is safe to use with fish eggs and fry.
  • Can be used to reverse nitrite and cyanide poisoning since it converts methemoglobin to hemoglobin, the normal oxygen-carrying molecule in fish.
  • Made in the USA and comes in an easy-to-use bottle and can treat up to 240 gallons.

Instructions

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Questions & Answers

11 Customer Questions

This is what I use when I change the water correct? I know there are a bunch or other stuff but they can also be pricey and I have to buy a few other item and this one seem to have everything I need to the tank just need to make sure I use it when changing the water? Thank you Gigi

Answer by Chewy • Apr 16, 2018
At the conclusion of all treatments, a partial or complete water change should be made and activated carbon replaced in the filter.

Can this be used for 20 gallon tanks

Answer by Chewy • Sep 10, 2018
This treatment can be used in all ponds, fresh and saltwater aquariums. To aid in general disease prevention, detoxification of fishes suffering from nitrite or cyanide poisoning and for use as a prophylaxis against fungus infections of fish spawns (eggs), add 10 drops per gallon (3.78 liters) or 1 teaspoon per 10 gallons (37.8 liters) of water (this produces 3 ppm methylene blue).

I recently bought two parrot fish. Both seem to have fungus on their body. Will this help it cure it? I know it’ll prevent but will it cure it if it’s there before hand? Should I also move the two parrot fish from the community tank they’re in or can I can do the treatment in their community tank?

Answer by Chewy • Nov 26, 2019
Kordon Methylene Blue General Disease Prevention Aquarium Treatment can be used to cure fungus as follows: For use as a dip, prepare a non-metallic container of sufficient size to contain the fish to be treated by adding water similar to the original aquarium. Add 5 teaspoons per 3 gallons of water. This produces a concentration of 50 ppm. It is not recommended that the concentration be increased beyond 50 ppm. Place fishes to be treated in this solution for no longer than 10 seconds. Return fish to original aquarium.

if u put this in a tank with goldfish will it cure ich? and help the fish get rid of the ich?

Answer by Chewy • Aug 23, 2019
This treatment is suitable to treat some external protozoans like Ich, Chilodonella and Costia, and provides protection to prevent infections.
Reviews
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4.7
Rated 4.7 out of 5 stars
29 Ratings
Terms & Conditions

8 Customer Reviews

Rated 3 out of 5 stars
By Sean on Aug 25, 2025

Bottle leaked during shipping

Once I cleaned the bottle I was able to use it

Once I cleaned the bottle I was able to use it

Rated 5 out of 5 stars
By lindsey on Mar 10, 2025

Does it Work?

I don't know if it works, if I'm using it right or what. I know for sure, wear gloves and clothes that you don't care about lol. Easy stain

I don't know if it works, if I'm using it right or what. I know for sure, wear gloves and clothes that you don't care about lol. Easy stain

Rated 5 out of 5 stars
By Keli on Oct 29, 2024
Top 1000 Contibutor

Does what it’s supposed to

I bought this, hoping that it would help the fishy smell, but it’s coming from my fish tank. Unfortunately, it did not. However, none of my critters have any type

I bought this, hoping that it would help the fishy smell, but it’s coming from my fish tank. Unfortunately, it did not. However, none of my critters have any type of disease or bacteria.

Rated 5 out of 5 stars
By S on Oct 25, 2024

Good quality for fish.

Safe for the fish. Good quality for fish. Did you as many drops just a few until the water turned a dark blue.

Safe for the fish. Good quality for fish. Did you as many drops just a few until the water turned a dark blue.

Rated 5 out of 5 stars
By Joy on Jul 9, 2024

Good medicine

Great medicine for fish illness or disease

Great medicine for fish illness or disease

Rated 2 out of 5 stars
By Chancyb on Sep 3, 2019

Didnt work for us

This product did not cure my bettas fin rot. Acually made him worse, I about lost him due to this stuff. Be careful when using it and make sure your fish has oxygen

This product did not cure my bettas fin rot. Acually made him worse, I about lost him due to this stuff. Be careful when using it and make sure your fish has oxygen while using it.

Rated 5 out of 5 stars
By Anna on Dec 26, 2018

good product

Have used Methylene Blue for years to treat common fish problems. My local pet store does not carry it so I was very happy to find it at Chewy.

Have used Methylene Blue for years to treat common fish problems. My local pet store does not carry it so I was very happy to find it at Chewy.

Rated 5 out of 5 stars
By Donna on Sep 11, 2018

Thank you Chewy !!

I have been raising Koi and fancy goldfish for years. Methylene blue is a MUST HAVE for koi and goldfish eggs. Stops the growth of fungus that eggs are susceptible

I have been raising Koi and fancy goldfish for years. Methylene blue is a MUST HAVE for koi and goldfish eggs. Stops the growth of fungus that eggs are susceptible to as well as fungus and other diseases on aquarium fish. Use in ponds or aquarium or as a dip when fungus appears. Sometimes when a fish is injured a thick white cottony fungus will grow on the injury. Methylene blue is the perfect product for that. I've used it as a dip mixing enough to make the water dark blue and I've used it on larger fish by taking the fish out and putting methylene blue right on the wound. You will literally see the fungus come off. Also works on; ick without burning like malachite green will, ammonia poisoning (red streaks on gills or body), nitrite poisoning (gasping for air tan or brown gills), velvet, and some cases helps with swim bladder disorder. EXCELLENT PRODUCT !!