What is This?

[jboi]

I was looking closely this evening in my aquarium and spotted 4 of these little guys. What are they? They were not there a few days ago.

 

[Sugar Magnolia]

Well, given the picture, they are likely fan worms, which are harmless. Can you post more pics? The reason I ask for more pics is they could also be rock dwelling sea cucumbers.

 

[jboi]

Thanks for the reply. I wish I could take better pics, but I tried with my iPhone with the same result as I posted. These guys are quite small. About 2-3mm wide. I found more and seem to be concentrated on just 1 rock.

Very cool!

 

[Sk8r]

Yep, just part of a useful biodiversity.