Looking closely at the image you can see tiny little brown spots on my tang. Heís acting healthy, but those little brown spots are a little concerning to me cause he acts fine but dosnt seem 100% healthy. Could it possibly be ick?
Has it grown or changed shape since it appeared? Could be a bruise or an injury that happened during collection. Is it flashing or doing anything that would be considered as abnormal behavior?
EDIT: So, I found your second thread. It obviously has gotten larger, but could still be a bruise. Can you provide us with more information about the fish, other livestock, parameters, anything that could assist with ID'ing the issue at hand other than seeing some possible bruising from something?