Something is gathering shells and rubble

[Aquavaj]

Never paid much attention to these things but did start noticing my empty shells and small rubble getting placed around the center front of my tank. It looked unnatural so I then spread them randomly around the front of the tank. Then the other day I noticed again they were at the very front center of the tank but now they were lined up in almost a straight line and pretty evenly apart.
I guess it's possible it's the powerheads but I would think that will cause them to just cluster up and not be in a straight line fairly evenly apart. Here's a picture.

 

[Reefer911]

Maybe something inside is trying to send you a message. Weird for sure

 

[Reefkeepers Archive]

Spread them FAR, then come at night with a red light and see if you can catch it in the act. Could be a wrasse or a triggerfish, do you have any of those? Looks like something a fish would do

 

[Mr_Knightley]

I've seen hermits slowly aggregate shells into a single 'shell stash' before, but never that fast. I suggest you take a look after lights out, I would love to see what it is who's doing this!

 

[SpursFan]

I've had that happen a few times but it's usually a back corner, just hermits doing their thing.

 

[Aquavaj]

Spread them FAR, then come at night with a red light and see if you can catch it in the act. Could be a wrasse or a triggerfish, do you have any of those? Looks like something a fish would do

I have a leopard wrasse but it's usually somewhere in the sand before my lights are even out.