Trichlorofon (Masoten)

Trichlorofon is an organosphosphate. It is available under its trade name Bayer Masoten or Dylox. It is found as an ingredient in pet store medications such as Dylox or Anti-Parasite. It is in Aquarium Products Life Bearer and the same company's Applus+ Anti-Fluke and Clout.

It is dangerous to both humans and animals and has been banned in many countries. In humans it causes neurotoxic poisoning. Repeated doses may build up in the flesh of fish and prove fatal or injurious. There are safer alternatives. However, the alternatives are much more expensive.

We do not recommend this drug. It is included in the library because it has been a popular treatment for flukes and other parasites. According to Thomas Giovanetti in Discus Fish (Barron's), tests showed that some strains of flukes have developed such resistance to Trichlorofon that the flukes survive a high dosage and the fish die! However, many parasites have developed drug resistance to Trichlorofon. Praziquantel is a more effective and safer medication.

Action

The drug affects the nervous system, thus vital physiological processes.

Effective Against

Used to treat monogenean flukes, Gyrodactylus (skin fluke) and Dactylogyrus (gill fluke), as well as leeches and crustacean ectoparasites. Argulus (fish lice) and Lernaea (anchor worm), Trichodina spp. Ergasilus spp.

Treatment Regime

Masoten is considered more effective in a long bath rather than a short one. The author has not tested it on guppies, and it may be too toxic at higher concentrations (3 mg./ liter for 3 days). Catfish may be particularly sensitive to it.

Suggested concentrations:

0.25 mg trichlorofon per liter in temperatures below 27C

0.50 mg trichlorofon per liter in temperatures above 27C

0.4 mg Mastoen per liter in temperatures above 13C

Make a stock solution: 1 g Masoten to 1 liter water. Residues must not be dumped down the drain. They need to be neutralized by raising the pH above 12 with sodium hydroxide for two hours.

Once mixed with water, the solution must be administered right away...a couple of hours and the solution may be toxic.

Treat for three days and then move the fish to a parasite-free tank. The treatment tank is bleached and let dry for three days.

According to the Extension Service at Auburn University, the dosage for Masoten for the treatment of Gyrodactylus, Cleidodiscus, Argulus (Fish Lice), Achtheres (Gill Maggot), and Ergasilus (Gill Louse), is 1/4 - 1/2 ppm for one application. Which is 0.6 - 1.2 gram per 500 gallons.

Avoid inhalation or contact with the skin.

Masoten may be stressful to guppies. If dosages are exceeded it can be highly toxic.

Masoten must be stored in a cool, dry place in an airtight container. It absorbs moisture, breaking down to a substance toxic to fish. It may be better to purchase it new. If you do store it, you need to make sure that atmospheric moisture cannot reach the powder. Store it with a desiccant, like silica gel. The gel can be regenerated by spreading it on a tin baking sheet and heating for about 15 minutes at 105 to 110 degrees C. When the moisture is driven off, it turns blue again.

Where to Get

Trichlorofon is slightly bluish powder that is unstable in water and lasts less than a week when stored mixed with water. It is available as a liquid called Neguvon, which is an 8% solution in a stable liquid format. In some countries it is illegal to buy or use it.

If bought in the powder form, and it looks wet, lumpy or translucent, it has degraded to the toxic Dichlorvos and should not be used.

Trichlorofon is found in the very common and readily available pet shop product, Aquarium Products "Life Bearer." Recently Aquarium Products repackaged the product and sold it in a larger size, calling it Applus+ Anti-Fluke. It is also in their product Clout.

Trichlorofon is an ingredient in Jungle Labs Gold Care Parasite Care, along with diflubenzuron.