What should I do?

[djtuzik]

About 3 weeks ago, I brought home a hippo tang. He was in QT for two weeks, all good. I brought him in to the display after two QT weeks, he started scratching on the rocks. I took him out, he seems to have stopped or the scratches are not getting any worse but there are scratches near it's gills. He eats well and swims around.
My other fish in the DT looks great, eating and no ICK.

How long does it take for white spots to appear after scratching? Could it be something else?

 

[Dmorty217]

QT for 8 weeks, not 2. Are there others in the DT? Sounds like the DT has ich...

 

[djtuzik]

yes, other fish are in DT but not showing and signs of the sickness

 

[Dmorty217]

The ich is there even if you don't see signs. Your choices aren't many. Getting all the fish out and leaving the tank fallow for 73 days while treating all the fish in another tank is the only solution. I'm sure people will mention hypo but I wouldn't do it