Gill Flukes, Skin Flukes of gold fish and koi
The descriptions of the common fish diseases have been deliberately kept simple to assist the understanding of the basic problems that may be encountered. This is a fascinating aspect of pond keeping and massive amounts of resource for further study can be found across the Internet.
The key to disease control is observing gold fish or koi behavior. Any lasting changes to normal behavior should be investigated because this is the first indication that something in the pond might be wrong.
A correct diagnosis normally needs more in-depth examination often using a microscope.
Flukes ... Freshwater flukes are microscopic in size and are reported as Gill Fluke, and the second class is the Skin fluke. Gill flukes lay eggs and the rate of egg laying is a function of pond temperature ... low temperature slow rate and vice versa. The incubation within the egg is also temperature dependent.
Flukes attach themselves to hosts in the gill region.
Skin flukes produce live young which immediately infect the host. rate of reproduction is very high.
Flukes feed on blood and mucus close to the surface of the fish's gill or skin. Skin flukes are happy to reside in the gills as Gill flukes are to live on the skin. They use hooks and/or suction to remain attached to the host.
Flukes survive in 0.3% salt solutions. The main cause of fish deaths seems to be related to secondary bacterial infection from Aeromonas and Pseudomonas types.
The oxidation and disinfection characteristics of Potassium Permanganate are able to control flukes at the level of 0.2%Some recommend the use of formalin but this has a severe negative effect upon bio filter bacteria and should be avoided if possible.