What is this? Looks like chaeto but it's not

[pikachux3]

Left is chaeto, right is some sort of algae that grows on my rocks. Very similar to chaeto but thinner and seems to grow attached to the rock. Can't seem to find anything on Google matching it's description. Definitely not hair algae and doesn't have fronds

 

[Webslinger]

my chaeto grows on rocks....Actually my royal gramma picks it and makes his home bigger with it