[Delphinus]

Unmistakable I'm afraid. Your fish has skin/gill flukes. It's not too bad at the moment but you need to treat him with Prazipro.

It's pretty much a given nowadays that, in particular tangs and angels, should be assumed to come with flukes. It's my opinion that everyone should have a bottle of Prazipro (or Praziquantel powder) on hand.

The good news is that it's treatable. The bad news is that if it is NOT treated, it can get into their gills, and will then likely be fatal. And it can spread to your other fish. So treatment, is, in my opinion "mandatory."

Prazipro is about as reef safe as you can get. I did lose my abalone during a praziquantel treatment but it's possible that he was on his way out anyhow (he was 5 years old) so I'm not sure if it was related or not. However, all my corals, all my clams, all my other snails, all my fish - all survived the treatement. The tank did look like crap for a week with film algae on the glass going out of control, so it's not a painless week, but it's a worthwhile pain to endure for the sake of your fish.

I will dig up some threads you can read for further reading and post back when I have them. Good luck!