Yellow Tang, it's not very visible during normal running of the aquarium, unless you have auto-lights on.
I first noticed it back when the Starfish was released when I turned down the lights to try getting it to crawl up on the glass. With the lights all down, the Royal Gramma's fin was sticking out like a sore thumb, as if it was radioactive or something.
Maybe it should be renamed the "Royal Gamma". Hehe.
