Prevents fungal infections on fish eggs Treats nitrite and cyanide poisoning in fish Treats fungus and external protozoan parasites on fish Methylene blue is commonly used by fish breeders to prevent and treat fungal infections on fish eggs, as well as treat fish with cyanide and nitrite poisoning. As a secondary use case, it can help treat superficial fungus and some external protozoan parasites on fish. The disease symptoms can include white tufts or strands on the body (fungus) and scratching on the tank bottom or objects (external parasites). Ingredients:— Contains zinc-free, chloride salt of Methylene Blue in a 2.303% water solution— Very stable in this solution, even when exposed to sunlight— Not intended for human consumption so store the bottle away from children Each bottle contains 4 fluid ounces (118 mL) and treats 240 gallons. Methylene blue may stain the silicone sealant in aquariums, so consider treating the fish in a catch cup or hospital tank rather than the main display tank. Manufacturer's Directions for Use For All Treatments:— Methylene blue is best used in a bare aquarium or pond, since it can disrupt beneficial bacteria and plant growth — Before using the medication, remove any chemical filtration (like activated carbon) and porous materials (like driftwood and rock)— Once the treatment is complete, a partial or complete water change should be made and activated carbon replaced in the filter. 1) For Prevention or Treatment of Fungus on Fish Eggs:— Add 1 teaspoon of methylene blue per 10 gallons of water to produce a 3 ppm concentration. To increase the concentration by 1 ppm, add approximately 1/3 teapsoon (1.64 ml) per 10 gallons of water.— Only one application is needed. Treatment should continue for 3 days past the free swimming stage or for livebearers 2 days after birth.— Make a water change as noted and replace the filter carbon at the conclusion of the treatment. 2) For Prevention or Treatment of Fungus or External Parasitic Protozoans:— Add 1 teaspoon of methylene blue per 10 gallons of water to produce a 3 ppm concentration. Continue the treatment for 3—5 days.— Make a water change as noted and replace the filter carbon at the conclusion of the treatment. 3) For Treatment of Nitrite or Cyanide Poisoning in Fish:— Add 1 teaspoon of methylene blue per 10 gallons of water to produce a 3 ppm concentration. Continue the treatment for 3—5 days.— Make a water change as noted and replace the filter carbon at the conclusion of the treatment. 4) For Use as a Dip to Treat Fungus, External Parasitic Protozoans, or Cyanide Poisoning:— Prepare a nonmetallic container of sufficient size to contain the fish to be treated by adding water similar to the original aquarium.— Add 5 teaspoons (24.65 ml) per 3 gallons of water to produce a 50 ppm concentration. It is not recommended that the concentration be increased beyond 50 ppm.— Place the sick fish in this solution for no longer than 10 seconds.— Return the fish to its original aquarium.