Whats on my sponge?

[Callen]

My sponge is a different color now. It was just a creamy white, now looks like a rusty colored dust on it. Ive got the same dust on my power head and I just pulled it out and wiped it off. Tried to blow it off the sponge but it is there to stay. There are some teeny tiny snails that like to hang out on it though. Maybe cyano? But it isn't slimy as most have described it to be.

Here are before and after pics. I've rearranged the rock so the after picture looks from a different angle.

 

[Sniperhank]

Looks dead and detritus is building up on the new rockwork.

 

[Callen]

Where is the detritus? I always thought detritus was fish poo!

 

[Sniperhank]

That or diatoms.

 

[Callen]

But where do you see it? On the rock? I'm not sure what to look for.

 

[Sniperhank]

In the second picture, the rock is white. When coral dies the skeleton turns pure white. The brown color on it is the build up, which is a diatom bloom. It'll go away once the silicates are consumed from the sandbed.

 

[Callen]

Ooh ok. I'm actually starting to think that particular "rock" is actually an old/semi-dead sponge itself and perhaps the one that is growing in my pic is from a few cells that survived somehow.

I bought it online as tonga live rock and overall I have been very happy with the variety of shapes and colors. A lot if it looks like it was coral though. This particular rock is pure white inside. I can see it in a few places where it has broken off and this type of sponge is sprouting up in a couple of places on it.

Thanks for your help. I mistakenly thought diatoms were the brown crumbs on the bottom of my tank. They are the brown powder that is on the sponge too?

 

[Sniperhank]

Pretty much.

 

[54seaweed]

could try blowing it off with a turkey baster

 

[Animal-Chin]

is that sponge soft? To me it looks more like dead encrusting coral than sponge. If it's soft (like sponge) then ok but if its hard I'm going with dead coral that is now getting some algae on it...

 

[Callen]

No, it's not soft. It is as hard as a rock but I do think it has grown since I first noticed it. I really don't know what it is, I posted a pic and someone told me it was a sponge.