2023 Quarantine Procedures Jay Hemdal David Scarborough Protozoans (Cryptocaryon/ich, Amyloodinium/velvet) and Metazoan trematodes/flukes are by far the most common parasites found on newly acquired fish. A carefully managed quarantine process can effectively eliminate these parasites before...
A tang without a quarantine process more than likely is ich. You can run a uv sterilizer immediately at the proper flow rate or like the member mentioned, copper safe / copper power is your best method to mitigate the disease.
if you plan to quarantine this fish, ensure all other fish are quarantined as well. Otherwise when placing back in display the other fish are still infected and the QT is for nothing
This is most probably ich. If you can get a clearer picture with less blue light, I can better confirm that.
Assuming it is ich, the number of spots present tends to indicate that you may need to treat this and not try to manage it in the tank (through UV, stress reduction, etc.).
Are there other fish in the tank?
Any spots on them?
How long as the blue tang had these spots?
Did you see the spots come and go at first?