Fish Lice (Argulus)

Fish Lice (Argulus)

Argulus another crustacean parasite, round and up to 1cm wide. They have a sucker to hold on to the Koi with needle-like mouth parts which they stick into the Koi and inject a toxin. This causes intense irritation to the Koi and they scratch and jump and can cause bacterial infection. The punctured areas of the koi will also be open to secondary bacterial infection.

This parasite can be introduced to the koi pond by visiting frogs and toads.

Argulus reproduce by laying eggs. After mating the female detaches from the host koi to deposit her fertilized eggs on the pond walls or any other surface. Upto 500 eggs may be laid. Dependent on water temperature the eggs take between two and four weeks to hatch. The newly hatched parasites will swim to find a host koi. They will reach sexual maturity after 20 to 50 days depending again on the water temperature of the pond, then the cycle starts again.

To treat an Argulus outbreak you will need to sedate and inspect every koi in the pond, removing all adult parasites with tweezers. The pond must then be treated to kill off the juveniles. This treatment should be repeated two or three times at intervals of seven to ten days. The most effective treatment is Masoten.

See More Koi Diseases

Anchor Worm

Anchor Worm

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Chilodonella

Chilodonella

Chilodonella cyprini. Chilodonella is another protozoan parasite which effects the skin and gills of koi.This koi parasite is typically between 40 and 70 microns in length and is oval in shape. Again, identification of this parasite can only be achieved through the use of a microscope. The parasite multiplies quickly ...
Costia

Costia

Ichthyobodo necator (Costia) This koi parasite is extreamly small (10-20 microns long) and a magnification of 100 times is the absolute minimum required to identify costia, 400 times is ideal. When taking a skin scrape and looking for Costia, try to avoid using a thick layer of mucus and add a drop or two of water to the slide. Cost ...
Cotton Wool Disease

Cotton Wool Disease

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Dropsy

Dropsy

Raised scales (rather like a pine cone) and eyes standing out from the head. Dropsy itself is not a disease, but rather a result of some other cause. Dropsy is a term given to the swelling that occurs internally in the fish. There are multiple possible causes. Sometimes it's not contageous, but sick fish should be isolated and treated s ...
Finrot and Ulcers

Finrot and Ulcers

A number of bacteria are associated with finrot, lesions and internal hemorrhaging, notably Aeromonas and Pseudomonas. Ulcers usually start at the site of an injury, the bacteria then infect it causing further damage, and fungal infection can also occur. Such holes result in osmoregulatory problems, leading to damaged kidneys and death ...
Gill Maggots

Gill Maggots

Gill maggots are the mature females of the parasitic crustacean Ergasilus. Ergasilus (gill maggots) will appear as grayish black and white parasites several millimeters long infesting the gills. Heavy infestations can cause severe damage, eroding the gill filaments and allowing secondary infections to develop.
Saprolegnia Fungus

Saprolegnia Fungus

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 ...
Skin and Gill Flukes

Skin and Gill Flukes

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 ...
Trichodina

Trichodina

Trichodina is one of the easiest protozoan parasites to detect under the microscope as it is almost perfectly round with hundreds of hooks which resemble cilia found its periphery and it constantly rotates as it moves through the mucus, causing tissues damage. It attacks both skin and gill tissues of our Koi, and can often cause more d ...
White Spot (Ich)

White Spot (Ich)

Caused by Ichthyopthirius multifiliis. The white spots on the skin, gills and fins are individual protozoan cells that are under the skin and feed on the body fluids and cells. They then punch out of the skin and fall to the bottom of the pond, collect together and begin breeding, the offspring then re-invest the fish. As well as white ...