What are these spikey red things?

[uncwalley]

I have these wierd spikey red things covering a rock that once was covered with zoos. One has managed to spread to another rock, but for the most part they are stationary. I don't notice any movement in or around them. Any ideas?

 

[chevegan]

either a sponge or a type of algae. Either way they are harmless from my experiences

 

[waterfaller1]

Foraminiferans.

 

[dendro982]

Could be a red foraminifera, Homotrema rubrum. The Shimek's article is here .
Database link , in French, but understandable.
Mine:

 

[uncwalley]

Good call dendro. Thanks.