Are you sure the spots are blue? Could they be white? What size are they? How long have you had the tank and is it heated, filtered and cycled? How long have you been keeping fish?
What are the readings of
ammonia, nitrites, and nitrates in your water?
If they spots are white, then you need to start to slowly raise the temperature of your tank to 85 degrees F (a degree every other hour or so) and leave it there for a solid 14 days. Treating for
ICH. If you do this put the other fish back into the tank so they are all treated as if one of them has it in the tank they will probably all end up with it. There is no medication needed if it is ICH just the raise in temperature.
If possible please respond with the answers to the questions.
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Rose