Invert ID help

I have seen this on the back of my tank for a while now, and I thought it was a sponge. My wife noticed the tentacles last night. It's about a half an inch across, and is sessile. Any help on what this is? Sorry it's so fuzzy. The camera focused on the coral on the right I guess. 

 

i know there is a type of jellyfish that are like that im trying to find the stuff i have read on them before

 

It's spherical, about the size of an acorn. It looks like a sponge with the vents.

 

http://atj.net.au/marineaquaria/hitchhikercnidarians.html check this out i think they are called Hydroids might be wrong

 

I'd venture a guess of a hydroid also: http://www.reefs.org/library/aquarium_net/1097/1097_2.html

 

I believe it is in the sponge/tunicate family. Its a circular mass with holes that will send out "fingers" to objects around itself in order to secure its position. It doesnt hurt anything. I think you can find an picture id and info in Julian Sprungs "Invertebrates" book. Im sure someone in the club has one that you could borrow? Goodluck

 

Tina, your description is right on. I'll keep doing some research. Thanks for everyone else's input. I'm sure it's not a hydroid. More ball like than anemone like.