Yellowtail Damsel acting weird!

[chazz66]

Recently I saw my yellowtail damsel swiping sand out from a cave area in my LR.She would back in and swish her tail to knock sand out of the area. Could this be some sort of nesting? I do have a pair in my 55 FOWLR. :notsure:

 

[aqua39]

I am experiencing the same thing with my yellowtail, it is a loner, with only on other species of damsel in my tank.