attached to rocks

Attached Chaetomorpha antennina is the first image on Wikipedia's Chaetomorpha page How many of you all have come across attached Chaetomorpha, in captivity? When I was figuring out macroalgae with my first build years ago, I discovered that Chaetomorpha is capable of attaching itself to rocks...

I keep finding these white fuzzy type things all over my rocks and I’m concerned about what they are, hopefully you can tell what they are in the pictures, if not I will try and take better photos