Koi Health

Warning

Some of these pages contain graphic images of Koi deformities. Viewer discretion is advised.

One of the most common fungal infections of Koi. The fungal spores will grow anywhere on the Koi, including the gills, initially germinating on dead tissue. Their threadlike hyphae release digestive juices which break down the tissue so the fungus can absorb it, as the fungus grows these juices start breaking down living tissue.

Fungus on the body appears as cotton wool like growths, it is hard to tell if a Koi has it in the gills, but if it hangs at the surface gulping for air it is likely.

Carp pox. A virus that produces solid waxy lumps on Koi. It will not kill Koi and is generally harmless, but can look unsightly. It is most often present in small Koi and in cold weather, clearing up disappearing when Koi grow and in the spring when water temperatures rise.

Gill and Skin flukes are two of the family of monogenetic trematode genera, all of which are characterised by the large grappling hooks which are used to attach themselves to their victims.

Affected Koi often exhibit classic signs of irritation and flash, jump or rub themselves against objects in the pond in an attempt to rid themselves of their attackers.  
Flukes are not visible with the naked eye.  When viewed under a microscope, the parasites are clearly visible as nearly transparent and worm like, and the hooks are clearly visible.

 

Gyrodactylus (skin fluke) 
 
Gyrodactylus is one of two common worm type parasites which the koi keeper may encounter. The parasite is worm like in shape and it has hooks with which the parasite attaches itself to the koi.

This koi parasite reproduces live young. Being hermaphrodites, all of the adults are capable of producing young, and each one will carry a single larval parasite in its abdomen. Further more, this unborn parasite is also developing a larval parasite in its abdomen before they are even born, and in as little as one day after being born, those young can also give birth. So it’s easy to see that this koi parasite is very prolific, and one individual is capable of reproducing into thousands in a short period of time. When viewing this parasite under a microscope you can often see 3 or 4 developing parasites within each other.

Once this parasite is attached to a host koi, it lives and feeds on the mucus skin and blood of the koi. The parasite is capable of surviving without a host koi for five days.

This koi parasite can be treated using Kusuri Fluke M.

 

Dactylogyrus (gill fluke) 
 
This koi parasite is very similar to Gyrodactylus in appearance. It has a set of hooks with which to attach itself to the host koi and these are surrounded by a number of smaller hooks.

The two parasites differ however in their method of reproduction, this koi parasite is an egg layer, and can lay up to two- dozen eggs per hour. Water temperature is important as the reproductive rate increases in warmer water, and decreases in colder water. The same applies to the time required for the eggs to hatch. In warmer water hatching can take only four days, whilst in colder water it may take as long as thirty days. This is a very important fact to remember when treating this koi parasite as most treatments will not kill the eggs, and they can hatch even after treatment and re-infect the fish. For this reason either the initial treatment has to stay active for at least four days, or you must do a second dose of the treatment.

To treat koi infested with this parasite you will need to use Kusuri Fluke M, take further skin scrapes to ensure all parasites have been eradicated.

One of the most common fungal infections of Koi. The fungal spores will grow anywhere on the Koi, including the gills, initially germinating on dead tissue. Their threadlike hyphae release digestive juices which break down the tissue so the fungus can absorb it, as the fungus grows these juices start breaking down living tissue.

Fungus on the body appears as cotton wool like growths, it is hard to tell if a Koi has it in the gills, but if it hangs at the surface gulping for air it is likely.

Carp pox. A virus that produces solid waxy lumps on Koi. It will not kill Koi and is generally harmless, but can look unsightly. It is most often present in small Koi and in cold weather, clearing up disappearing when Koi grow and in the spring when water temperatures rise.