Single white object on tang dorsal

[Sierra_Bravo]

I noticed what initially appeared to be a single white circular spot on its dorsal. Upon closer inspection this morning it is now a larger irregular shape. Whether that changed from last night or I just couldn't see it well enough I'm not sure, but I do believe it was circular when I first had seen it. There is nothing else present on the fish and the fish is eating and acting normally.

Fish has been in QT for 8 weeks. I did not perform TTM or treat with copper. Fish has only undergone Prazi, metro and kanaplex treatments during the time it has been in there. The metro and kana was used because I had mistakenly allowed the salinity to rise to 1.030 two weeks ago while on a business trip and the tang showed signs of stress. I wanted to prevent any potential infections from occuring.

Opinions on what it is and what I should do next?

 

[EmdeReef]

Sounds like lympho. There is no cure, but keeping stable params and feeding high quality vitamin enriched foods helps speed up healing. Give some nori as well.

 

[Sierra_Bravo]

Sounds like lympho. There is no cure, but keeping stable params and feeding high quality vitamin enriched foods helps speed up healing. Give some nori as well.

I was actually hoping if it was anything at all it was lympho. However, I have been very fortunate in that I have never experienced ich firsthand and wasn't sure if when the trophants leave the fish if they left behind a residual cyst casing or shell and that was what I was seeing. I'll give it a couple more days and continue to observe.