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The ciliated parasite Ichthyophthirius, more commonly known as white spot or Ich, is a very common fish disease capable of affecting virtually all fish species. Ich has a fairly complex life cycle that has a major bearing on treatment methods. The white spot trophont (photo below) forms a nodule under the skin or gill epithelium. If you see signs of this disease treat immediatly. Signs of this disease are listed below.


Identifying Ich


White spot cysts, each containing an active trophont, appear as small white nodules on the skin, gills and fins, giving the fish the appearance of having been dusted with salt. In a confirmatory skin scrape the trophonts appear as dark round objects slowly rolling around. The trophonts vary in size, up to 1mm and are considerably bigger than most fish parasites.


In the early stages of the disease, fish are likely to flash and rub against objects because of the irritation. At a later, advanced stage they will become lethargic and spend most of their time sitting on the bottom.



There are two main approaches to curing whitespot, and opinions vary on which is the more effective. There are several effective commercially available remedies, normally based on malachite green and formalin. Note that malachite green is hard on scaleless fish like catfish and loaches, and also other fish such as tetras. Some alternative medications are based on copper and formalin. The other method employed is to add salt to the tank (gradually), up to a level of 6-8 tsp per gallon. Note that fish vary in their tolerance of salt, and for more sensitive soft-water species, it may be better to use 3-4 tsp per gallon maximum. Higher salt levels may also affect plant growth.


In either case, increasing the temperature should kill the parasite off more quickly, because it will speed up the life cycle of the parasite, so that the free-swimming stage is reached as quickly as possible - this is the only stage affected by medications. However, increasing the temperature means there will be less oxygen dissolved in the water (some medications can lower it too), so ensure the tank is well aerated, and do not raise the temperature beyond around 28oC (82oF).


Due to the life cycle of the parasite, the whole tank must be treated, in order to kill the parasites which are not attached to fish. Therefore it is not appropriate to treat only the affected fish in a separate isolation tank.


Effective commercial remedies include Protozin by Waterlife and Maracide by Mardel Labs.


My own experience is that Ich commonly affects koi and clown loaches - but in the early stages the characteristic white spots are very difficult to spot. They are probably there but not very noticeable.


Please post more information and experiences you have!

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