My Gem tang keeps going back and forth in the back of the tank, sometimes darting and flashing and attacking the glass. It looks like he’s fighting his reflection. All the other fish including several tangs in my 625g just kind of look at him like he’s nuts. Has anyone had a fish do this for a long period of time. Seems to happen worse when the lights are on as this is when the reflection can be seen more vividly. Any suggestions as I’m afraid he’s going to die from exhaustion and self inflicted stress! Thx