Final answer:
The characteristic symptom of ich in fish is the presence of white dots on the body.
Step-by-step explanation:
The characteristic symptom of ich in fish is the presence of white dots on the body. Ich, also known as white spot disease, is caused by a parasite called Ichthyophthirius multifiliis. This parasite attaches itself to the fish's body and causes small white spots to appear, resembling grains of salt. These white spots can be seen on the body, fins, and gills of the infected fish.
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