You may want to be aware that most fish carry the plain 'ich' parasite forever and never fully get rid of it. It is usually brought out by stress and other factors. I had small break outs on my tang in my old tank. I just made sure to feed him well and the spots would go away. I never treated with anything.
QT'ing the fish is a good idea, though. Ich only becomes a major problem when tangs get a really bad case - other fish are pretty resilient. The spots could literally be gone in a day or two. If it were me I would do water changes, feed the fish well, and watch it disappear in a few days. Ever situation is different though!
How are your water parameters and what are you using is measure salinity? I found that high nitrates and out of whack salinity (I was using a swing arm, which are horribly inaccurate) brought out the ich in my tang.
What size tank do you have and what fish are in it? That ich came out for some reason or another.
55 gallon, i have a pair of black clowns, a pearly jawfish, 6 line wrasse, dragon goby, and the royal gramma.
I use a swing arm deal too, and i run my salinity a little high (about 1.026 or 1.027, just inbetween)
I've only ever tested my water twice, the 2nd time being not even a week ago. pH was good, no nitrates or nitrites...
I just did a water change saturday, added a skimmer friday. I noticed when i was putting the pump for the skimmer in the gramma was freaking more than the other fish, can it pop up that quick?
All of my fish eat very well also.
Good info anyways, hopefully its just an outbreak only in the gramma due to the stress of me movin around rocks and puttin that pump in there and not an immanent fish holocaust.....