It is said that this parasite can be commonly introduced into our koi ponds by frogs and toads. It is however easy to detect with the naked eye especially against the background of fins and white skin of affected koi. Size varies from between 1mm and 5mm. Attaching themselves to the koi by suckers which damages the skin, they also inject a poison into the body of the koi which causes inflammation, bleeding and potentially secondary bacterial infection. Pale green in colour, juveniles are more transparent.
Argulus must be eradicated quickly as the parasite causes considerable physical damage to the skin which often results in subsequent ulceration of the affected areas if left untreated.
Chemical treatments recommended to eradicate these parasites are either Dimilin or Paradex. As the parasite is easy to spot with the naked eye, physical removal is suggested before chemical treatment to remove as many as possible from affected Koi.