White spot on my tang

[jroescher]

I have a white spot growing on my yellow tang. The tang is about 3". The spot is on very tip end of his pectoral fin. It's probably tripled in size since I first noticed it several weeks ago. It looks like Ich, but it's only one spot.

Any ideas? This is the best I could get for a picture. The tang refuses to pose long enough for me to photograph it. Hopefully you can at least see the size of it.

Added another picture.