Need help with identification

[Rdp122]

Hi, I need to figure out if the thing in my tank(blue stringlike projections growing on the Rock in the background) is detrimental to the lifespan of my fish.
Thanks

[cloak]

Picture?

Can you remove them with a brush easily? Dark string like projections growing from the rock could be Dinoflagellates, but without a picture it's kind of hard to say.