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, collect together and begin breeding, the offspring then re-invest the fish.
As well as white spots symptoms are scratching and swimming into the water inlet, failure to feed and lethargy. It is fatal if untreated. Fortunately commercial white spot remedies are widely available.
Classed as a large protozoan parasite, white spot must initially be detected through the use of a microscope, however if left, its effects becomes identifiable with the naked eye. Koi infected by white spot appear to be covered in white spots the size of salt grains, where the parasite has burrowed through the outer skin layer.
To multiply the adult parasite leaves the host koi, it then forms a capsule around itself. Within the capsule it divides and multiplies producing up to 1000 tomites (babies). These are then released as free swimming parasites to go in search of a new host koi.
This reproductive cycle is rapid and so early detection of this koi parasite is essential.
To effectively eradicate this koi parasite we recommend using a treatment which is a mix of formaldehyde and malachite green. Pre-mix solutions are available, but it is better to mix your own as the dose rate of formaldehyde should be altered dependant upon pond water temperature.
White Spot Video Clip 1 White Spot Video Clip 2