[James]

O.k. what is this? it looks alot like a big spiderweb. I noticed it growing on the underside of my live rock. Anyone seen this before, or know what it is? sorry about the pix, they are not that great.

[zhenya]

Hi James,

From the pic it looks like a sponge to me. I have those as well and they seems to come and go. I suppose the conditions in that spot are favorable for it and it will persist as long as it can and then just be gone one day. Nothing to worry about,IMHO.
Here's a pic of mine that has been in this spot for about 5 month or so.I know that it will be gone in a while and then something similar will sprout in some other spot. I personally think that it is a sign that your system is maturing.

[Samper]

The rock that my mushroom polyps came on has various growths similar to what you guys have shown. I do notice that they seem to move around like sort of spread and recede over time. Some of them have holes that looks like a tube or something comes out of but I've never witnessed anything coming from them. Neat to watch, nothing to worry about IMO.

[zhenya]

Originally Posted by Samper

Some of them have holes that looks like a tube or something comes out of but I've never witnessed anything coming from them.

Those tubes are part of the stracture of the sponges, they are filterfeeders after all Not much will come out of it, in my case an occasional tiny brittle star will crawl out of or simply stick out one of its arms. I have a picture of this somewhere, if I find it I'll post it here.

[Samper]

Would be neat to see Gene.

Thanks

[Dragonmoray]

Looks like a chicken liver sponge (Chondrilla Sp.)

[Clay12340]

Out of curiosity Zhenya on the left middle of your picture there are a couple pink tubes like people have been talking about in this thread, but do you ever see the sponges attached to them grow spines?

I have one of these pink sponges that has been growing on the rock for some time and last week it spent a couple of days looking more like an urchin than a sponge. It has gone back to normal now, but I was curious as to why it might have done that. Any ideas?

[zhenya]

Originally Posted by Clay12340

Out of curiosity Zhenya on the left middle of your picture there are a couple pink tubes like people have been talking about in this thread, but do you ever see the sponges attached to them grow spines?

No, I haven't noticed any spines or transformation that would resemble that pattern.
Here's an interesting article written by Dr. Ron Shimek on sponges and if you haven't read it I highly recommend it.

As the coral growth increased.., I can hardly see any of the sponges behind them.Taking pictures of them is out of the question altogether.

[Clay12340]

haha, I'm going to stop reading next time I see Shimek's name on an article. Every article I read just tells me that whatever I thought I knew was completely wrong. Yesterday he ruined my supposed understanding of live rock and today sponges.

[zhenya]

Originally Posted by Clay12340

haha, I'm going to stop reading next time I see Shimek's name on an article. Every article I read just tells me that whatever I thought I knew was completely wrong. Yesterday he ruined my supposed understanding of live rock and today sponges.

I'll pass it along next time I talk to Ron...
If it's any consolation, it happened to me as well when I first read his articles. Blew my knowlege base clean out of the water...