Aquarium Fish Methylene Blue

Butterflyfish swimming above coral in an aquarium

Methylene Blue (also known as methylthioninium chloride) is a photosensitizer, cationic dye, and redox indicator. It is utilized as an antifungal and anti-parasitic in aquaculture, and it is often used to treat fish eggs to prevent fungal overgrowth. Methylene Blue is a safe disinfectant for aquariums that may also be used to cure ammonia and nitrite sickness.

Uses

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."
  • : 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.
  • : Also known as Velvet, this is actually caused by a parasite.
  • : Fish struggles to maintain proper position, floats upside down, swims with tail higher than the 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.

Safe Applications

Crustaceans, such as crabs, shrimp, and snails, can be given Methylene Blue, but it must be done cautiously. It will harm living plants and should be used with cautiously in such situations, with plants exposed for short periods of time.

Methylene Blue should not be used with Erythromycin or Tetracycline at the same time. Wait 30 minutes after applying a Redox lowering water conditioner (which includes most water conditioners) before adding Methylene Blue. During treatment, stop using carbon media in filters since it will eliminate the Methylene Blue.

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Fungus on Fish Eggs

For prevention or treatment of fungus on fish eggs, follow these instructions for treating your aquarium with Methylene Blue:

  1. Remove carbon from the filter and continue to operate with mechanical filter media.
  2. 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.
  3. Only one application is needed. Treatment should continue for 3 days past the free-swimming stage or for livebearers 2 days after birth.

External Parasitic Protozoans

If your aquarium is affected by a fungus or by external parasitic protozoans, apply Methylene Blue using the following steps:

  1. Remove carbon filter and continue to operate with mechanical filter media throughout the treatment period.
  2. 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.
  3. Make a water change as noted and replace the filter carbon at the conclusion of the treatment.

Nitrite or Cyanide Poisoning

As an aid in reversing nitrite (NO2−) or cyanide (CN−) poisoning of marine or freshwater fish, use Methylene Blue in the following application:

  1. Remove carbon filter and continue to operate with mechanical filter media throughout the treatment period.
  2. 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.
  3. Make a water change as noted and replace the filter carbon at the conclusion of the treatment. parasite protozoans."

Use as a Dip

You can also use Methylene Blue as a dip for treating fish with fungal infections, those affected by external protozoan parasites, or those suffering from cyanide poisoning.

  1. Prepare a nonmetallic container of sufficient size to contain the fish to be treated by adding water similar to the original aquarium.
  2. 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.
  3. Place fishes to be treated in this solution for no longer than 10 seconds.
  4. Return fish to the original aquarium.

Products

Fish Vet Methylene Blue 

Instructions for use: 1.25 oz. dropper bottle 1 drop per gallon is the recommended dosage. After 3 to 5 days, perform a 25% water change and replace the carbon. Continue treatment 2-3 days after the fish are free-swimming if used as an egg fungus preventive.

Dosing instructions for powdered concentrates: Remove the lid and slowly pour water into the bottle. To blend, replace the cap firmly and shake gently (we recommend using Reverse Osmosis or Distilled water). 1 teaspoon for every 10 liters After 3 to 5 days, perform a 25% water change and replace the carbon. Continue treatment 2-3 days after the fish are free-swimming if used as an egg fungus preventive.

Discontinue carbon filtration but keep all other filtration running during treatment. Replace carbon after treatment.

Kordon / Oasis Methylene for Aquarium 

Directions for Use from the Manufacturer: Freshwater and marine aquariums and ponds should use the following protocols. Porous materials like rock, coral, and wood may absorb Methylene Blue. It's preferable to utilize the product in naked aquariums or ponds, especially if they're brand new. Methylene Blue may stain aquarium silicone sealant permanently. A partial or total water change should be performed after each treatment, and the activated carbon in the filter should be replenished.

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