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, Acriflavine and strong salt baths of 3% ( 4 and one half oz. per gallon )
Summer usually means increased pond water loss due to evaporation, which of course leads to topping off our ponds more. You should always add dechlorinator when topping off the water level of a pond. Any amount of chlorine (such as that found in treated water) can be harmful to your fish. Even if it is not enough chlorine to mean immediate death of the fish, this chlorine can still cause harm to proper gill function.
