Emerald Crab picking at bare rock?

[ZzyzxRiver]

My emerald crab is scraping at a shadowed part of my rockwork that has zero algae on it (and there is plenty of algae for her, she's doing a great job on it). Theres a little pile of rubble gathering under her and lots of it out in the water column. I don't even have a good hypothesis for what the reason could be. It's somewhere she hangs out when she's not eating, but she has plenty of secure hidey-holes all over that she uses, too. Has anyone experienced this kind of behavior before?

 

[Dread Pirate Dave]

I haven't seen that but there must be something there that she is after. (I would think)

 

[paragrouper]

I have three emeralds constantly picking at the rock work. Half the time, my tired old eyes can’t see what they are after.

 

[ZzyzxRiver]

I haven't seen that but there must be something there that she is after. (I would think)

I assumed there was something minuscule…. I wish I spoke crab, I would direct it one inch over to the hair algae LOL

 

[bhotep]

I assumed there was something minuscule…. I wish I spoke crab, I would direct it one inch over to the hair algae LOL

My emerald crabs love to eat the coraline algae off my rocks!