Need some help here, is this some kind of Algae?

[reefjonny]

Is this a type of algae? It's under many if not all of my rocks and is purple in color:

 

[Mastiffsrule]

Evening,

Picture is a bit fuzzy for me, but I am thinking a sponge. Look close at them, see if you can sny tubes coming out. Like little snorkels. I have them in my tank, but green. .