Aiptasia or something else??

[amphicar77]

Hi All,
I have noticed two types of small "things" growing on a few spots of my live rock. Not sure is these are aiptasia or something good.
The first looks like a small black urchin. I think he actually came on the back of one of the snails and has now attached himself to the rock.
The second seem to live in small holes in the rock and are between a transparent and a very light green color. They are very small, essentially round, sort of made up of 2-3 cocentric rings where the outer ring is slightly feathery. I did notice that if I point my laser pointer at them that they very quickly pop back inside the holes in the live rock. I thought perhaps aiptasia but the pics I see of that appear to usually be more of a brown color.
Do I leave em or try to kill em off? Since they are very small, shoudl I wait till they get bigger before deciding. Might try to take a picture later but really not sure if it will come out.
Thanks.

 

[amphicar77]

On closer look, and in looking at other pictures, I became pretty sure my "urchin" was an aptasia as it was more brown than black and had the longer tentacle type arms like I have seen in the pics. He thus met a syringe of boiling water. I am still not sure what the other guys are, the do look different than the first.

 

[kiharaconn]

The second thing that you asked about sounds like small feather dusters. I have several in my rock that are a ring of white and a ring of green and also some that are brown. Also several in the sand that are rings of purple and white. They are light and movement sensitive. They are filter feeders and are ok for your tank. You can purchase larger ones that are quite pretty and add some different textures to the tank. The small ones don't get very large, about the size of you little finger nail but the larger ones can get very large.
Enjoy them.