Some sort of like weird tube thingy.

[jonnywater]

These tubes are like a reddish gray. They are nearly hard as rock too. Some of them have poppep up on my clams and some just on the LR, basically any hard surface. But I nearly need my propogation sheers to break them up because of the thickness. They are kind of swirly too. This is the best pic I could get, any ideas??

 

[romeofoeve]

i get them on my lr and sometimes on my frogspawn and hammer corals, it affects the corals. i looked under the hitchhiker id thread:
Vermetid Snails: These are another common filter feeder found in many tanks. They are actually a sessile snail. They grow in dark red and brown spirals and tubes, usually on live rock. They vary from a few millimeters to ½ an inch or more in length. Some cast out small mucus nets in order to capture food. While they are harmless, the mucus nets can sometimes be an eyesore.