Strange Spawning?

[The Kapenta Kid]

I noticed some some tiny white objects like threads of cotton fluff floating about in my tank. While I was inspecting them a jet of them was auddenly blown out of a small hole (about 1/8 to 1/4 inch diameter) in a piece of live rock. A minute or two later another jet of them was blown out. I can best describe it like the jet of spores that is ejected by a ripe puff-ball fungus--except they emerged from a hole in the rock.
Under a strong lens the white threads look like commas with a feathery almost transparent fan-like structure attached to the dot of the comma.
Any ideas?

 

[djconn]

Do they move on their own? If not, my suspicion is a sponge.

 

[The Kapenta Kid]

Do they move on their own? If not, my suspicion is a sponge.

Good sherlocking! :mrgreen:
Nope, they don't move on their own and they emerged from that circular hole directly below the blue hitchhiker sponge.