Mysterious animal growing on rock

[Gouramiboy9142]

Hey guys! So I looked in my aquarium this morning and found some strange looking critters growing on some of my rocks. They were very small, white, and shaped like grains of rice with little paintbrush-like bristles/fringes on top of them. Fearing they could be a potential pest, I gave my rocks a scrub-down, and hopefully removed all of them. How they entered the aquarium is beyond me, however, as there isn't really a way that they could have - I obtained all of my rock as dry rock, none of my hermit crabs or other inverts seemed to be carrying any, and the aquarium does not currently have any corals. Anyone have an idea as to what these could be? Thank you in advance!

- Diego

 

[Gouramiboy9142]

Update: So I saw there are actually a few of them left over that I had missed. Anything to be worried about? Thanks again in advance!

- Diego

 

[Sniperhank]

Harmless filter feeders. Just tube worms.