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.
See More Koi Parasites
Identification of Koi parasites. Most koi parasites are not visible to the naked eye. In order to correctly identify any koi parasites you will need a microscope with built in light and a magnification of 400... (click on image for more details)
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... (click on image for more details)
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... (click on image for more details)
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... (click on image for more details)
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... (click on image for more details)
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,... (click on image for more details)
Lernea (Anchor Worm). This koi parasite is most commonly found on newly imported koi, and should be dealt with by your koi dealer, it is rarely a problem for the koi hobbyist. It is visible to the naked eye and... (click on image for more details)
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... (click on image for more details)
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... (click on image for more details)
Columnaris (Flexibacter columnaris) or Cotton Wool Disease is another bacterial infection. The common name comes from the white tufts that develop around the mouth and spread to the body and fins, often leading... (click on image for more details)
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... (click on image for more details)
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... (click on image for more details)