What is this??

[NYfan78]

Its on the bottom of a rock that forms a top of a cave. Its white, looks soft not hard. Shaped like a upside down volcano. its left of the shrimp!

[Chad]

I can't see it well, but it's either a sponge or a tunicate (probably sponge). Tuncates are like little water pumps and have an inlet tube and an outlet tube. If these are visible, it's probably a tunicate. If there is just one opening, it's likely a sponge.

[NYfan78]

so no need to worry then?

[Swimboy123]

Nope, they are good for your tank

[Coral Hind]

It looks like a sponge forming to me. It will help to clean your water.

[NYfan78]

SWEETNESS!

[ToddR]

Looks like a sponge. Great to have in a reef tank. They regularly shed collar cells which are great food for SPS.

[Steve175]

A free and benign reef gift. It is still my favorite part of the hobby when random cool things just pop up.

[jaddc]

It is amazing how many eggs/cysts sit dormant on rock for a long time and then start growing when the conditions are right.

[Origami]

Yep, looks like sponge to me.

[Coral Hind]

Here is some nice info on sponges.

http://reefkeeping.com/issues/2005-06/rs/index.php

[jaddc]

Also, you have some nice encrusting sponges on your rock, so its not surprising that another one is growing. If you ever take your rockwork apart you will most likely find more of those guys.

 

J