My Pinktail does the same thing, just looks bored sometimes....LOL
I just put some CC in a glass bowl because my tank is BB, & for days it has entertained itself with that. Moving the CC out of the bowl, rubbing in it & even biting the glass... I guess what ever floats it's boat.
My Pinktail is in my 300g, I see you have a " 540 gallon with a 200 gallon sump under construction", so it may do the same in that tank.....
I Put Nori on a clip sometimes (I feed Nori Daily) just so it can be entertained tearing the clip in 3 or 4 pieces....LOL
Kaye