Parasites are an major cause of fish diseases. It is almost impossible to keep fish free from parasites, but with regular repeat microscopic examinations parasite outbreaks should be kept to a minimum. A healthy Koi housed in optimal water conditions without overstocking should be host only to a minimal amount of parasites. Stressful conditions such as poor water quality and over crowding will lower the immune system and the koi will become liable to disease.

Haphazardly administering preventive treatments without prior examination is not possible and is not advised. As there are so many parasites, each with specific treatments that preventative treatment is impossible.

Parasite	Identification	Treatment
White Spot	more details	formaldehyde and malachite formulation, Treatment for White Spot is temperature related. At 25C treat twice four days apart, at 18C treat twice six days apart and at 10C treat twice 10 days apart.
Costia	more details	potassium permanganate or formaldehyde/malachite, one treatment should be sufficent
Chilodonella	more details	as above
Trichodina	more details	potassium permanganate
Flukes	more details	formaldehyde/malachite or Supa Verm