Are these sponges ?

[kronin]

Hello all,
Ive been baffled for a few weeks now as to what these creatures are. The two pictures included show two different specimens. There about 1.5inches across, and are soft/rubbery to the touch, not hard like a shell.
They seem to be a sort of network of semi-opaque tubes. I actually have about four that I can see.
So Im always looking up sponges in books and on the net to see if theres anything that they could be - what do you think ?
Thanks.

 

[up north hermit]

Yes, some sort of sponge. I have lots of them in my 40 reef, some are actually getting quite large and very attractive under my VHO lighting. A beautiful irridescent green.
I just discovered a new pale pink one on the backside of a LR, with a feather duster growing right out of the middle of it!
My only negative about them is they seem to light really lower light, so they are not readily visible unless you know where they are at.
Good pictures Kronin.
HTH
Hermit
P.S. Not sure, but could this be some sort of sea squirt maybe? I wondered this as well.

 

[kronin]

Thanks for your help Hermit - I thought they were some sort of sponge.
Ive got a few more aswell that are a bright green/yellow colour. I agree that those look very nice.
Should I expect them to grow any larger?
Thanks again

 

[up north hermit]

Yes, some of mine are about 3" across, and now have several tubes growing out of the mass instead of just the one they started with. These are feeder tubes. I suspect as the mass grows it needs to provide itself with more nourishment. My theory of course
I love to study them under my magnifier, the ones close to the glass I can really get to see. I also have some small ones starting on my powerheads!
Good Day!
Hermit