Please help identify weird formations

[kernnell]

Please help identify these weird formations, they are similar to short wite hair, medium hard and break up easily if touched. Them they stay in the water column for a while and settle down or get skimmed. They are usualy covered with some kind of slime, that I blow off my corals using a seringe. It almost killed my GSP and other corals as well. It took me some time to notice, bacuse the slime blends very well with the rock, its kind of a grey / light brown colour.

In the photos you can see them wright after the slime was blown off with the syringe water jet

 

[Vinny Kreyling]

Filter feeders of some sort, I used to have them in a sump.

 

[kernnell]

Normally they are not like that, this is sort of the skeleton that remains after blowing off the slime that hides them