Need ID on this worm - or whatever it is.

[scantech]

This "worm" is living in my tank. It comes out at night. By day it looks like a fuzzy cocoon hanging on the underside of the rock. It can come out about 4-5" in length from what I have seen. Not sure if it is harmful to anything, should I leave it or remove it?

 

[LeslieH]

That's a digitate hydroid. Depending on the species - and none of us here can identify them - the impact of the nematocysts may range from mild to very toxic & harmful. If you find that animals within range of it are affected then pull it. I don't know if they spread rapidly. Hopefully other people who have had them can join the discussion about whether to leave it or not.

 

[mndfreeze]

They do spread rapidly if there is food available for it to eat, and by food I mean anythin git can grab it seems. They are growing in my tank out of control at the moment. I paste over bad ones. Can never seem to kill them any other way.

The ones I have can't hurt my SPS, dont seem to hurt my acans, but jack my zoa's up bad.