Any ideas what these things are?

I returned from a 6-week overseas trip to find that my tank was doing great -- lots of coraline algae, no unwanted algae, and all my fish and inverts were healthy. But, I noticed these Unknown Tiny Creatures under some of the rock ledges and in the shadows.
Here's a picture:


They are very small, less than 1 cm, and there appear to be dozens. I only noticed when I took some pictures that there are even more creatures that are too small to see without magnification. They are white, almost translucent, and appear to have bristles/feelers/tentacles at one end. The base of each creature is firmly attached to the rock.

Do any of you have any theories on what these Unknown Tiny Creatures are?

 

Here's another picture. Larger versions of the pictures are in the photo gallery.


That's the tip of my finger on the right side of each photo, so you can see that they are not even as long as my fingertip is wide.

 

Ive seen them called sponges and sea squirts, either way, they are beneficial filter feeders.

 

I'm not sure. They're the right size, but they don't have the dual siphons that tunicates have. However, one of the larger ones (not pictured) appears to be budding, so this may be the development of the second siphon.

 

lol Ive seen them called tunicates too. Either way, they are beneficial. Its hard to know for sure what anything is when people reference non marine biologists.

 

Look here, it might be this. http://www.3reef.com/forums/inverts/cocoons-42544.html#post384882

 

Might be some form of nuisance/invasive sea squirt --- if so, you may have real problem on your hands.

Check out:

Ciona savignyi (Solitary sea squirt)
Animal Type: Tunicate/Sea-squirt
Family: Cionidae
Classification: Unlisted Invasive Species

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Hermit Crabs may eat them.

 

I think there called pineapple sponges ( well thats what we call em anyways)

 

Well, the picture provided are sponges. Harmless, but they will grow everywhere so keep up with cleaning your equipment.

You have translucent life, as well? Could be a tunicate. Really, if you are concerned about anything becoming invasive, do a little googling, see what conditions these sorts of things thrive in and see if their are any adjustments you can make.

 

+1...that's what I've always called them