comAnchor worms (Lernae):
Anchor worms are one of the most ferocious parasites that can attack our fish. The cling themselves with hooks in the skin tissue. Because the anchor worm pierces a hole in the fish it causes a wound which can get infected by bacteria or fungus.
The most common leech for Nishikigoi is the fish leech (Piscicola geometra). This leech is long shaped and can grow up to 5 cm. Once attached to the Nishikigoi they penetrate the skin to suck the blood. The health of a leech-infested koi can deteriorate rapidly. The koi can get anaemic. Besides this the koi is more vulnerable to other infections.
Carp or fish lice (Argulus):
Is a circular shaped parasite. Adult Argulus measure about 10 mm. It is a very common parasite. Both the larvae and the adults have an sting which injects digestive enzymes into the body. They then suck out the liquidized body fluids with their proboscis-like mouth. Reddish inflammations appear that, when not taken care of, can cause secondary infections. Fish lice can cause so much irritation that koi will rub and flash and can even jump out of the pond.
Skin fluke (Gyrodactylus):
Gyrodactylus trematodes is a viviparous (live bearing) fluke of 0,3-0,5mm that can procreate rapidly. The fluke attaches its hooks in the skin of the fish thus causing irritation. The fish will produce more mucus.
The gill fluke is egg bearing. It damages the gills which can no longer function well.
Nematodes are worms that live inside the fish. Both the larvae and the adult cause serious infections in the internal organs, thus disturbing their proper function. At the start fish will emaciate rapidly. Then they will become lethargic, show signs of exhaustion and lose their appetite.
White spot disease (Ich):
Probably the most well-known disease, caused by protozoa with cilia all around. Ich seizes its opportunity if fish have a decreased immunity, if water temperatures change rapidly, if filtration is changed, to many cold water when filling the pond, contamination due to new fish, or if the present filtration system is not in optimal working order. Poor water quality as well as stress are very important factors
This parasite mainly occurs on the skin and gills. It uses the fish for transport. During the transport it attaches itself to the fish and by doing so, damages the mucus layerof the fish. Pond water of poor quality is a very good environment for the Trichodina parasite.
Protozoa that can cause grey areas that after a while will turn red and in a later stadium can cause bloody wounds. Usually this wound is covered by a fungus. Sometimes Costia is found on the gills. The death rate from Costia can be very high, because bacterial infections also often occur. The fish tumbles, grates and in the later stadium will emaciate. Fish will become restless, have difficulty breathing and tend to surface whilst gasping for breath.
Oval shaped protozoa. In case of mass infection this parasite is lethal. It mostly occurs on the gills. Transferring is the main cause of immediate outbreak. Any fish that is in weaker condition, can cause mass reproduction of this parasite.