I have a Hippo Tang (Blue Tang, Indo-Pacific - Paracanthurus hepatus), about 3-4 inches long.

A few days ago I bought a Copper Banded Butterfly (first fish added in 3+ months) and everyone got VERY excited about the new "Invader". My powder Blue was being a royal pest, and all the other fish were really "on edge" for a few hours.

My Blue tang came out and I noticed the "Non-Blue" markings didn't look right, it looked sort of pale or copper'ish :o At that moment it didn't strike me that these markings should have been "Black", I just new they looked odd. An hour or so later he was back to normal (Blue & Black).

Has anyone else seen this in a Hippo - do they have the ability to modify their color when threatened or under stress?