If there is one disease of freshwater tropical fish that every fishkeeper will have to deal with sooner or later, it’s ich. Ich (also referred to as white spot disease) is the shorthand name for Ichthyophthirius multifiliis, the organism that causes the problem. The reason ich (pronounced “ick”) is such a common ailment is that this organism is everywhere in aquatic environments; the encysted adult stage is not affected by treatments that eradicate the free-swimming infectious stage. All it needs is favorable conditions and fish with weakened immune systems, both of which are very common in the aquarium hobby.

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