@Doomzee 253d

They retract when I put my finger near them

@skebo 253d

My vote is for stinging cnidocytes. But I could easily be wrong. Let some others chime in.

@MaxB. 253d

Looks like hydroids to me, I had some of the same in my tank a while ago, never noticed any stinging of corals from them. Harmless in my experience.

@billy 253d

I would second hydroids

@SoothingGalaxy17 253d

looks like vermetid snails maybe!

@Doomzee 253d

No calcium tube. Have seen v snails in my tank before. Leaning more towards hydroids at this point based on appearance. Worried about spread of hydroids now I think

@CrimsonPetal65 253d

hope it clears up!

@ElectricDragonfly86 252d

hope it clears up!