Gill and Skin flukes are two of the family of monogenetic trematode genera, all of which are characterised by the large grappling hooks which are used to attach themselves to their victims.

Flukes are another common parasite affecting our koi are both egg layers and live bearers. They range from 0.05 to 3.00mm long and there are actually a huge number of species in the genus.

Affected Koi often exhibit classic signs of irritation and flash, jump or rub themselves against objects in the pond in an attempt to rid themselves of their attackers.
Flukes are not visible with the naked eye. When viewed under a microscope, the parasites are clearly visible as nearly transparent and worm like, and the hooks are clearly visible.

Flukes are a bit like fleas on dogs and cats and it is common to see one or two on a slide as a healthy Koi can control parasite numbers and their mucus helps prevent the parasite moving. Treatment is therefore only necessary if flukes are seen in numbers.

Chemical control of both types of fluke can be achieved with Chloramine T, Malachite Green, Formalin, or Potassium Permanganate. In order to kill all generations, repeat treatments may be necessary, the frequency being dependent on temperature and chemical used.