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Chilodonella Parasites in a koi pond

The Chilodonella fish parasite is a microscopic parasite at all life stages, so you won’t be able to see them on your fish with the naked eye. They will attach to your pets on the skin, gills or fins. Chilodinella fish parasites can cause havoc in a koi pond at any time of the year but is most prevalent in the spring, or cool water temperatures. Their optimum temperature is 40⁰-50⁰ F. Left untreated; Chilodonella can kill a lot of koi in a small amount of time.

The Chilodonella fish parasite is round to heart-shaped organism that is full of tiny bubbles. It resembles an onion with tiny roots on one end. It punctures and feeds on the skin of its host to feed leaving behind tiny abrasions where bacteria can enter and cause secondary infections on koi and goldfish. Many times fish suffering with Chilodonella will rub or scrape pond edges in an effort to rid them, but instead cause more damage.

What are the symptoms of Chilodonella on koi?

If you have Chilodonella on koi in your pond you will notice the fish acting itchy or flashing and definitely being lethargic. Many times infected koi will lie on their side on the pond bottom, and then quickly turn upright when startled.