Koi

Although it is perfectly possible to have a parasite-free pond, there is always a risk of parasites being accidentally brought in with new fish or their transport water.

Common Koi parasites are those that attach to the body surfaces (skin, gills and so on). These include various protozoa (single-celled organisms) and worm-like flukes. Virtually all these skin-dwelling parasites are invisible to the naked eye.

 Other Koi parasites include tapeworms (inhabiting the fish’s gut or body cavity), thread-like nematode worms (in the gut), and parasitic crustaceans, such as the disc-shaped fish louse (temporarily attaching to skin).

Often, the first sign of a looming protozoa or fluke problem is when one or more Koi repeatedly rub their flanks against submerged objects, or leap from the water. These symptoms can also arise from a water problem (such as high nitrite level) so always carry out water tests before considering parasites as the cause.

Commercial liquid remedies are available for treating common skin and gill parasites – these treatments are added directly to the water so you will need to know the volume of your pond in order to administer the correct dosage. Prompt treatment is important because many skin and gill parasites are highly infectious and potentially lethal. If parasite problems persist then consider having your Koi checked by a fish health specialist (ask your Koi dealer) – this should reveal which type of parasite is to blame, enabling the most effective treatment to be selected.

The risks of introducing parasites into the pond can be greatly reduced by obtaining Koi from a reputable dealer who practices good husbandry and proper quarantine procedures – try to get a recommendation from an experienced Koi keeper.
 

Written by Dr Peter Burgess

Photo courtesy of The Environment Agency