Fish Diseases: ICH or White Spot
Triggered by a deep-burrowing parasite, ICH--also called white spot--is a highly contagious and all-too-common disease that causes small white pustules on a fish's skin and gills. Affected animals may rub themselves against objects in the tank in an effort to stop the uncomfortable itchiness. Treatment involves isolation of the sick fish and medication.
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. Other features sometimes seen are a lighter, horseshoe shaped nucleus
and short cilia covering the entire body.
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.
Ich commonly affects koi - but in the early stages the characteristic white spots are very difficult to spot. They are probably there but not very noticeable. This is one reason why it is best to do a skin scrape when parasites are suspected - so that you know exactly what you are dealing with! Even finding one trophont warrants immediate treatment.
Treatments
Beware ICH can lurk in the background
Ich is most often brought into the tank or pond on new fish or plants. However, it is also believed that some survivors of an Ich infection can become latent carriers, with the parasites forming a latent stage at protected sites such as the base of fins or the gills.
Subsequent stress or poor conditions can awaken white spot to re-infect either its host or other fish. This certainly seems to be the case with koi, when often small numbers of trophonts are often found alongside severe fluke, Trichodina or Costia infestations, even in ponds which have not had any new introductions.
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