Purple Tang has a white spot help!

[toyencounters]

I have a purple tang its been in my tank for over 6 months! Its been ultra healty great eater but I noticed a white spot near his mouth about the size of a dime any ideas? water parameters are near perfect including a constant temp of 78 deg.

 

[toyencounters]

It looks almost as if the skin bleached out!

 

[Momma_Fish]

I am not wondering if it's Tang turbellarian disease. I know it's also called Black Spot disease, but I was reading a little about but they can be white spots, could be one or it could be many. Do a little research on it and see if it matches. I hope you can figure out what's wrong with him/her. It's always sad to see a fish go.