Question: What is Xterm and how should I use it?

Xterm is an organophosphate insecticide for fluke, anchor worm and fish lice on koi and goldfish. All manners of insects, snails and worms, but NOT for protozoal parasites like Costia, White Spot, Trichodynia etc.

Closely related to organophosphates like Dipterex, Masoten, Trichlorfon, Metrifonate, Dylox, Negavon, etc (more than 100 names) Very popular! But very dangerous in the wrong hands. For that reason we packaged it in a save volume. The advantage is it biodegrades in water within 24 hours.

Treatment for ectoparasites like Protozoa (Ichthyophirius, [white spot] Trichodina); Monogenea (Dactylogyrus [gill fluke], Gyrodactylus [body fluke], Benedenia, Cleidodiscus); broad spectrum anthelminthic; Cestoda; Hirudinea; Crustacea (parasitic copepods, Achtheres micropteri, Argulus foliaceusArgulus sp. [fish lice], Ergasilus sieboldi, Ergasilus sp.[gill maggot], Lernaea cyprinacea [anchor worm], Philometra sp., SalmincolaSinergasilus major); mollusca [snails]

Use Xterm when normal medication for fluke gets ineffective. Read article


It is imperative to follow the dosage as per the label on the bottel since it available in different concentrations.


Two follow-up treatments over two week period is normally recommended.


Do not treat below 18 deg C (fish cannot metabolise/excrete it fast enough)

Do not treat above 28 deg C (uptake rate is too high)

It may be more toxic to other aquarium fish, orfe and rudd - first test.

It is toxic to sharks (tropical fish).

It can be removed by activated charcoal.

Can be used with salt.

Work carefully with it like any other toxic compounds. Wear gloves and protection gear as recommended.

Shake the bottle.

Other information

Frequently used in Koi keeping because effectiveness against various flukes (both gill and body fluke), fish lice, anchor worm, Ergasilus. Also Cestoda (tape worms), Hirudinae (leeches) and snails. Preferred treatment for fluke on goldfish.

Will kill most insects and must be used with care for environment. Degrades quickly in pond conditions, but can cause disorientation and nervous disorder if used incorrectly (Overdose). Typical symptoms of overdosing in koi is a bent spine and nervous, wip-like swimming. The fish may recover over a period of a year or two, but mostly won’t. The effect may also get worse over time.

We found it very effective in combination with salt as a prophylactic “first treatment” after harvest from the mud dams. A cocktail of Xterm and 3 kg/1000 litre salt (sodium chloride) for the first day. Then check the next day for parasites to decide on further treatment, typically M+f (malachite green and formalin)

About warm water aquaria:

Our experience is with koi and goldfish, but our gut feel is that this temperature sensitivity to Dipterex is the reason that warm water aquaria has problems with it. The rate of metabolism varies with fish species. So working with this knowledge one can still use it quite effectively. If you want to kill gogo's like leaches and snails and water beetle etc in your tank, remove the fish to another tank (at same temperature) for 24 hrs while treating your tank. Remove any active carbon filtration and replace after the treatment. But if you want to treat for things like fluke or worms that are on the fish, move the fish into a clean tank, no gravel, no filter, only air, but clean water at same temperature, for 4-6 hours, and move it back to its home after treatment.


Sources: Personal experience and. various databases, articles eg

Herwig N (1979) Handbook of Drugs and Chemicals Used in the Treatment of Fish Diseases: A Manual of Fish Pharmacology and Materia Medica. Charles C. Thomas, Publishers, Springfield, Ill. p272.

PAN Pesticides Database. http://www.pesticideinfo.org/Detail_Chemical.jsp?Rec_Id=PC33346 Accessed 17/10/2014

PupChem. http://pubchem.ncbi.nlm.nih.gov//compound/5853?from=summary accessed 17/10/2014

Wikipedia, http://en.wikipedia.org/wiki/Metrifonate accessed 17/10/2014

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