Trematodes are tiny parasitic worms that are also called Flukes. The two main ones that affect Koi are Gyrodactylus (skin flukes) and Dactylogyrus (Gill Fluke). You can usually find both types on the skin or gills, their not picky of what they eat. The main difference between the two is that Gyrodactylus is a live bearer and Dactylogyrus is an egg layer. Gyrodactylus can produce up around 2000+ babies a month during the summer. Dactylogyrus can lay 2000+ eggs within a month in the summer too. Flukes live off of the blood and mucus of a fish. The usual lifespan for a fluke is 2 - 4 weeks in warm water. Although, this lifespan can be expanded in cold water. Trematodes, like any other parasite, can cause a secondary infection like Aeromonas.
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