there is a treatment in desease forum for blach ich (check it out.) formalin bath.
i have controlled it recently on my yellow with soaking the food in fresh chopped garlic for at least 10 mins, a UV sterilizer and time, Others may disagree with this methods im just saying mine was here stayed a week and is now gone. probably still in my tank waiting to attack again im sure but for now im good. i could not get him out to do the treatment other wise i would have, and planned on doing it this weekend but then this weekend it was all gone so im buying time and crossing fingers.
good luck