Out of ideas.

[fsjman]

add garlic to the tank and turn your heat up to about 81 or so I have two yellow, sailfin ,regal,miki,and brown tang in my 150 and had a ich outbreak at the first. I poured a full bottle of garlic in the tank and turned up the heat and have not had a sign of ich ever since .... ich hate the garlic . also my tank stunk of garlic till my first water change but they all lived also buy some Ocean Nutrition seaweed select with garlic added the tangs I have liked the brown algae the best Good luck