Koi Information » Koi Diseases and Parasites » Costia

Costia is a minute Flagellate with 3-4 flagella. It affects both the skin and gills of Koi, and reproduces itself by binary fission. Infestations of this parasite can appear very rapidly indeed, and Koi suffering infestations exhibit the classic symptoms of lethargy, clamped fins, rubbing and flashing and the skin can take on a grey white opaqueness.

Costia normally only affects fish that have already been debilitated by some other cause, and can often be seen on Koi as a secondary parasite.

A high magnification must be used to view these parasites (300 x) and staining is recommended for positive identification.

Recommended treatments include Potassium Permanganate, or Proform C.