Methylene Blue

aquarium fish
cuncon/Pixabay

Name: Methylene Blue

Other Names: Methylthioninium chloride

Action: Cationic dye, redox indicator, and photosensitizer. In aquaculture, it serves as an anti-fungal and anti-parasitic.

History & Uses

In the 1890s Methylene Blue was studied for its anti-malarial properties, leading to its use during World War I, and subsequently in World War II. It continues to be used as an anti-malarial to this day.

Used medically in a combination that is known as “Prosed”, which serves as a urinary antiseptic, urinary acidifier, analgesic, and anticholinergic.

It also is used to treat Methemoglobinemia, and has been used for over a century as an anti-malarial in combination with other drugs. In the past, it was also used to treat cyanide poisoning as well as carbon monoxide poisoning.

Recently it has been tested as a possible treatment for some cancers. Clinical studies are also underway that indicate Methylene Blue significantly slows down the progression of Alzheimer's disease. It is also used in some drugs to aid in determining compliance, as it turns the urine blue, indicating the medication it is combined with has been taken.

In aquaculture, it has commonly used to treat eggs to ensure they are not lost to fungal overgrowth.  Methylene Blue is also used for the  treatment of ammonia and nitrite poisoning, as well as an antifungal, anti-parasitic. It serves as an aquarium safe disinfectant. Disorders that Methylene Blue is used to treat include the following:

  • Nitrite poisoning - Fish gasp for breath, tan or brown gills, rapid gill movement known as "gilling"
  • Ammonia poisoning - Fish gasp for breath, red or purple gills, lethargic - may lay on the bottom, red streaks on body or fins.
  • Ichthyophthirius multifilis - Small white spots resembling sand, fish scratches against objects.
  • Oödinium pilularis - Also known as Velvet, this is actually caused by a parasite.
  • Swim Bladder Disorder- Fish struggles to maintain proper position, floats upside down, swims with tail higher than head
  • Egg Fungus - Serves as a safe and mild disinfectant for fish eggs.
  • Fish stress - Prophylactic treatment of fish under stress, usually due to being moved.

Methylene Blue can be used with crustaceans, including crabs, shrimp, and snails, but should be introduced carefully. It will damage live plants and should be used with caution in such cases, being used for only limited periods of time.

Methylene Blue should not be used concurrently with Erythromycin or Tetracyline. After using a Redox reducing type of water conditioner (which includes most water conditioners), wait for 30 minutes before adding Methylene Blue. Discontinue the use of carbon media in filters while treating, as it will remove the Methylene Blue.

Products Containing Methylene Blue

Fish Vet  Methylene Blue 

Manufacturer's Directions for Use:

Dosing Instructions: 1.25 oz. dropper bottle dosing instructions: Add 1 drop per 1 gallon. Perform 25% water change after 3 to 5 days and replace carbon. If used as egg fungal preventative continue treatment 2-3 days after fish are free swimming.

Powdered concentrate dosing instructions: Remove top and slowly add water to the top of the bottle. Replace cap tightly and shake gently to mix (We recommend using Reverse Osmosis or Distilled water).

Add 1 teaspoon per 10 gallons. Perform 25% water change after 3 to 5 days and replace carbon. If used as egg fungal preventative continue treatment 2-3 days after fish are free swimming.

Discontinue carbon filtration but keep all other filtration running during treatment. Replace carbon after treatment.
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Interpet Treatment No. 10 Methylene Blue
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Kordon / Oasis Methylene for Aquarium  

Manufacturer's Directions for Use: The following procedures are suggested for freshwater and marine aquariums and ponds.

Methylene Blue is removed by activated carbon filtration. It will also be absorbed by porous materials such as rock, coral and wood. The product is best used in bare aquariums or ponds, especially if they are new. Methylene Blue may permanently color the silicone sealant in aquariums. At the conclusion of all treatments, a partial or complete water change should be made and activated carbon replaced in the filter.
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Prevention or treatment of fungus on fish eggs:

  • (a) Remove carbon from the filter and continue to operate with mechanical filter media.
  • (b) Add 1 teaspoon of 2.303% Methylene Blue per 10 gallons of water. This produces a concentration of 3 ppm. For increased concentrations, add approximately 1/3 teaspoon (1.64 ml) per 10 gallons for each required 1 ppm increase.
  • (c) Only one application is needed. Treatment should continue for 3 days past free swimming stage or for livebearers 2 days after birth.

Prevention or treatment of fungus or external parasitic protozoans:

  • (a) Remove carbon filter and continue to operate with mechanical filter media throughout the treatment period.
  • (b) Add 1 teaspoon of 2.303% Methylene Blue per 10 gallons of water. This produces a concentration of 3 ppm. Continue the treatment for 3 to 5 days.
  • (c) Make a water change as noted and replace the filter carbon at the conclusion of the treatment.

As an aid in reversal of nitrite (NO2-) or cyanide (CN-) poisoning of marine and freshwater aquarium fishes:

  • (a) Remove carbon filter and continue to operate with mechanical filter media throughout the treatment period.
  • (b) Add 1 teaspoon of 2.303% Methylene Blue per 10 gallons of water. This produces a concentration of 3 ppm. Continue the treatment for 3 to 5 days.
  • (c) Make a water change as noted and replace the filter carbon at the conclusion of the treatment. parasite protozoans."

For use as a dip for treatment of fungus or external parasitic protozoans and cyanide poisoning:

  • (a) Prepare a nonmetallic container of sufficient size to contain the fish to be treated by adding water similar to the original aquarium.
  • (b) Add 5 teaspoons (24.65 ml) per 3 gallons of water. This produces a concentration of 50 ppm. It is not recommended that the concentration be increased beyond 50 ppm.
  • (c) Place fishes to be treated in this solution for no longer than 10 seconds.
  • (d) Return fish to original aquarium.