crushed coral w/ tenticles.... what is this?

[tru2037]

Hello everyone, I have searched and searched the forums for years now but have never seen what I've got here. They are small, almost look like a small piece of crushed coral, but with tenticle arms, and until a crash I never noticed them. When I had a crash, brown algea covered everything and these guys poked up on top of the film. They cover about the whole sand bed in the ref but in the main tank there seems to be only a few. Sorry about the pics but these guys are small and this is the best I can do.
The white rock looking things... They have 6-8 arms that lay flat on the surface spread out.

 

[fibinotchi]

Sounds like spagetti worms but I don't see anything in the pictures.

 

[flower]

I have a bright green version of them, it is a type of algae.