Emerald crab has calcium buildup?

[Meckel]

I have 2 emerald crabs in my tank and they seem to have developed a white calcium looking buildup. I will try to upload pictures later today but Im wondering if there is some type of supplement I'm missing that goes with dosing the daily calcium? In using B-ionic and all my levels seem great.
Any thoughts?

 

[Packersfan21]

It could be bleached corraline algae.

 

[mokeyz]

My emerald crabs have the same thing and it has never seemed to harm them - I also use B-ionic. Interestingly it doesn't happen to my red mithrax crabs...