How’s this? I did just witness my Blenny try and go on a tang murder spree. Could it be an injury?
Looks like a bubble which is likely the result of either mechanical injury or gas embolism in which the socket is the weakest part of facial area of fish. Assure there are not microbubbles in the tank from return pump or skimmer contributing to this. In one respect, you can wait, and observe and see if fish will release the pocket on its own or help it with application of Maracyn, Not Maracyn oxy in a separate tank.Anybody have an idea of what this might be on my tangs eye? It was literally not there this morning when I fed so it has popped up over the last three or four hours. I just noticed it. It doesn’t seem like it bothers him he still eating and cruising the tank like normal. 
Yes, injury, likely cause. Isolate blenny in sump or acclimation box
The tang has been messing with him for the last few days, and he always runs away, but just suddenly turned into a little murderous frog rocket. I literally watched him swim from a bed of algae on one side of the tank all the way to the other lol.
