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Trichodina is an external parasite which is commonly found on a koi, especially at times of temperature change. It is also found more profusely in poorly maintained systems where mulm and sediment have been allowed to build up in the pond and in the filter. Trichodina can not be seen with the naked eye and can only be accurately identified through a microscope. It looks like a small circle and it may be spinning and moving at quite a high speed. Inside the larger circle a number of hooks are seen. These hooks are used for attaching themselves to a host fish. It is said that Trichodina is perhaps overrated in its ability to kill fish. The secondary infections will however finish the job if allowed to continue without treatment. The acute irritation is normally the cause of self mutilation as the fish scratches and flicks. Trichodina will kill young fish. Large numbers can damage the skin and make it vulnerable to attack by bacteria. These bacteria may aid the reproduction and spread of Trichodina because the parasite will use the bacteria as a food source. Trichodina multiply by division and will swim from host to host. There are unconfirmed reports that Trichodina can form cysts (Encysting Protozoan).


Symptoms associated with Trichodina
  1. Koi under one year old are more susceptible to Trichodina infection.
  2. First indication of a problem is fish flicking and flashing.
  3. Damage caused on the fish because of flicking and flashing.
  4. Bacterial infections as well as fungal infections may occur.
  5. Fish floats/hangs near the surface of the pond.
  6. Some koi may appear emaciated with the body wasting away.
  7. Whitish appearance around the head area that may spread across the whole body.
  8. Koi may become lethargic and weak.
  9. Fish may be pulled towards the skimmer or drains.
  10. If Trichodina has spread to the gills, the koi will frequent around air stones or water returns.
  11. In some cases, the fish may shake its head as if it is trying to dislodge a blockage from the mouth.

Prevention of Trichodina
  1. Avoid frequent water changes by heating the pond during spring and autumn.
  2. Do regular inspections of the filter to ensure no build up of debris. Debris can contribute to heavy infestations.
  3. Trichodina may be introduced through new plants, new fish and live food.
  4. Disinfect nets, plants and live food.
  5. Quarantine newly purchased fish

Treatment of Trichodina
  1. Salt (some strains of Trichodina are resistant to salt)
  2. Potassium Permanganate
  3. Malachite Green and Formalin

Last Updated on Sunday, 11 January 2009 10:27