Elan,
The tang you have is a Powder Brown (
Acanthurus japonicus). Here's a picture I found of a White Cheek Tang:
http://a1272.g.akamai.net/7/1272/1121/20030320004020/www.***********.com/images/products/large/pw73941whitecheek_tang.jpg
I attached a picture of My Powder Brown Tang. I've never had any problems with him. He's never had any diseases.
Raise the temp to 83
Temprature only affects the speed in which the parasite multiplies. The lower the temp, the slower it multiplies. The higher the temp, the faster. C irritans optimum temp is actually 86 degrees. Any temp required to kill the parasite would also kill the host fish. The theory of raising the temp is only slightly affective as it will promote the parasites free swimming stage more often, making medications more affective. Hyposalinity will work no matter the temperature.
I attached a picture of my Powder Brown
Graham