What is this in my fuge?

[slideways03]

I have a HOB refugium on my 40 breeder and i have noticed a creature of some sort pulsing against the side of it... It almost looks like a jellyfish type pulsing. little bit smaller than a finger nail. I tried my best to capture a photo and video....Any reason to be concerned?

http://youtu.be/4BS7NQnXL-8

 

[Dakotah]

Looks like a small tube worm to me I have a ton in my refug as well. As far as I know their harmless their just a filter feeder.

 

[garys reef]

+1

 

[Geraud]

Those are hydroids. They have three different stages: the medusa stage where they are a small jellyfish, blueish in color, pulsing towards the surface. Then the stage where they are kind of transparent, more bell-shaped, and with tentacles, where they attack often to the substrate (http://www.thereeftank.com/forums/attachment.php?attachmentid=78145&d=1294500897). And finally the stage you can see in your picture (the non moving ones), as little white tubes with white "hair"-looking tentacles. As far as I know they are dangerous only for slow moving fish like dwarf sea horses.