ID Me Please

[Marco S]

I have several pieces of live rocks in my invert QT and while they are all really interesting, one piece in particular had a bunch of life on and in it including a few bristle worms that I decided to keep. When I set the QT up a few months ago I just mixed the salt in the QT before putting any inverts in it and the piece with all the life developed a large white spot on the bottom that looked like unmixed salt. A couple weeks ago that spot started to grow little tentacle like things and spread out.

Here is what it looks like today:

Anyone have any idea what this is?

 

[S-t-r-e-t-c-h]

Looks like a cryptic sponge more than anything.

 

[DharkaronReef]

Def sponges. I have them in the bottom of my rocks and are good for reef tanks.

 

[Marco S]

Looks like a cryptic sponge more than anything.

Thanks! Just wanted to make sure it wasn't some kind of algae that I needed to worry about.