What are these shells on my GSP?

[Army_of_mantis_men]

I have noticed these shell-like shapes on my GSP, what are these? Where do they come from, is it good/bad? Should I do something about it? The photo is taken in the morning before the lights turn on, when it comes out it looks healthy as ever.
Thanks!!!

 

[Doctor Derp]

Looks like tunicates

 

[Gumbies R Us]

Tunicates