I have a couple of these things growing in my tank. They look like a thorn bunch on a cactus. There are 2 feelers that reach out from the center I assume to gather food. The main body appears to be a glassy hair patch. Kinda like a fiber optic wire.

I have handled these rocks and have not been attacked by these growths, maybe just dumb luck, but they dont seem to eject the thorns. They are growing from Bali Alor (Indonesian) LR.

Thats all I can tell you about them.