Came home and noticed this a spot on my vlamingi tang. It seems to be a circular spot with a black outline and normal skin inside. It sort of looks like a worm under the skin but I can’t be sure. Can some help ID what this is and what measures need to be taken?
sal- 35.0
pH- 8.1
Alk- 10.0
Phosphates- 0.08
Nitrates- 12
Calcium- 460
sal- 35.0
pH- 8.1
Alk- 10.0
Phosphates- 0.08
Nitrates- 12
Calcium- 460