Anchor Worm

Crustacean parasite, Lernaea. The juvenile stages settle in the gills of Koi, when they mature they mate and the male leaves the Koi, the fertilized female settles on the body of the Koi and continues to grow, becoming the familiar worm shape....

Costia

Costia is a minute Flagellate with 3-4 flagella. It affects both the skin and gills of koi, and reproduces itself by binary fission. Infestations of this parasite can appear very rapidly indeed, and koi suffering infestations exhibit the classic symp

Cotton Wool Disease

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 to ulcers and a thin appearance.

Dropsy

Raised scales (rather like a pine cone) and eyes standing out from the head.

Fin rot & Ulcers

A number of bacteria are associated with fin rot, 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 o

Fish Lice

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

Gill Maggots

Gill maggots are the mature females of the parasitic crustacean Ergasilus.

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 ca

Skin and Gill Flukes

These are the fish equivalent of fleas.

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, colle