Help me ID this hitchhiker

Hey all,

recently I noticed a bunch of growths on my LR in my 20g reef tank. I
hunted around online and found a pic that resemble exactly what i have
on the LR.

http://www.wetwebmedia.com/lrfaq5.htm

unfortunately, this is just a pic with no explanation. They are little
puffy things with what looks to be a feather-duster like top.

Are these some sort of sponge? More importantly, are these beneficial
to the reef or shoudl i consider removing them?

any help is appreciated!