A whole book could be written about this particular parasite, so I will keep it brief to give evryone a basic understanding of this nasty little critter.
The Latin name for Whitespot is ichthyophthirius or “ich” for short. This literally means “ Fish Harvester”, which gives you an idea as to how devastating this parasite can be when present in your pond.
It can be difficult to detect on a scrape, because it barely moves and is easily missed unless you are familiar with its shape and behaviour. They are often mistaken as water bubbles. They do revolve slightly on a slide and usually have a horse shoe, peanut shaped nucleus inside the grey exterior, which is a much lighter colour. Stress and poor water quality are major factors in whitespot outbreaks.
Unlike other parasites, the whitespot does not attach itself to the outer skin layer, it burrows under the skin. We have to wait until the “ swarmers” hatch in order to kill them in the free swimming stage, they are not affected by treatments whilst on the koi. Initially, the trophont ( early stage whitespot), attaches itself and moves under the skin and when it has matured it breaks away from the nodule and attaches itself to something else,such as a plant, forming a capsule around itself. This is called the tomont stage. This tomont eventually hatches, producing up to a 1000 tomites, which swim away to find a host - your koi. These then burrow into the skin of the koi, causing serious infection, residing in the body, not out.
The life cycle varies depending on the water temperature, from 5 days at 25C, to six weeks at below 12C. This is why you have to adjust the treatment depending on water temperatures.
The usual symptoms are displayed by koi infected with whitespot, namely flicking and flashing, lethargy and heavy mucus. In the latter stages, small salt like deposits can be seen on the koi. Undetected, whitespot will kill your koi very quickly, so you MUST act quickly after it has been identified.
The favoured treatment is Malachite and Formalin mix, perhaps the only guaranteed effective, legal treatment. You should use 2% Malachite at 10ml per 176 gallons and 30% Formalin at 10ml per 140 gallons. Mixing it yourself is preferable to the premixed bottles available, but please wear protective gloves as Malachite is carcinogenic and Formalin is extremely dangerous to humans. Do not , under any circumstances, use an old bottle of Formalin that has “ crusted up” around the top of the bottle, as this is lethal to your koi.
Follow the directions stated by the manufacturer with regard to dosage, temperature and gallonage.
Other treatments may include;
Acriflavin with salt, and Malachite Green with salt. Some have had success with a prolonged salt dosage of 0.5ozs per gallon.