Help ID...Grey looking stuff

[Simba]

Hello...I noticed this on one of my rocks (the rock has two GBTA's on it). Does anyone know what it is...is it bad...how do I get rid of it? I would appreciate anyone's help. Thank-you!

(Sorry for the poor quality pictures)

 

[Genesis Corals]

Hard time telling what you are referring to in the photos. I know some sponges are grey in color and are slimy to the touch.

 

[Reefing Madness]

Bottom pic almost looks like Green Cyano.

 

[Simba]

Thank-you...I will be doing a water change tomorrow so I'm going to take the rock out and try to brush it off. I'm worried about the nem's but I'll try not to stress them too much. I'll post if I can get any better pictures.

 

[Mike J.]

Can't tell by your photos. I have some sponges that are gray, and, black, yellow, orange, purple, clear. Is it porous or can you see any siphons? Of course sponges are filter feeders and are not bad.

 

[Simba]

It was smooth looking...I didn't see any pores...I used toothbrush and it came off pretty easy...I hope it doesn't grow back. Now I'm waiting for my nems to get back to normal for them.