Airplane Pillow Looking Thing

[TYNWALD]

I discovered this yesterday in my 6 month old 200g tank. There is a stack of them on top of each other. Should I be concerned?

 

[Tahoe61]

Vermetid. I use superglue or epoxy. They can bother corals. The population of vermetid is determined by the available food source. Suspended particles in the water column, that includes food and detritus.