Algae? White stuff on rocks

[NadiaG]

I put these rocks couple of weeks ago and they now have a white stuff ( some green) on them. I changed lighting recently and that def speed things up. Is it algae, mold, bacteria? Safe or harmfull? Will otos eat it?
Thanks in advance!!

 

[NadiaG]

I vacuumed the gravel and rocks and some of it came off..