Id good or bad?

[gashunk]

So I found these things in my tank on. A piece of lr and I got no idea what they are they do have semi long tentacles and they are clear

 

[bayoupr]

Hard to tell from the picture but from your description, sounds like aptasia. Bad for corals, will sting your corals if the corals grow too close to these. I would remove the rock and replace it. Do not try to remove these by hand, if they break up they will spread to other areas of your tank.

 

[Tahoe61]

They also look like they might be Hydroids. Touch one, a Hydroid will withdraw the tentacles, an Aiptasia will completely close up.

 

[twilliard]

Yup looks like colonial hydroids
Superglue them before they get out of hand