Grey sack like substance on live rock??

[rmor22]

I saw a really good looking piece of live rock at my LFS but it had a 5 or six grayish-blackish sack like substances on it. They are about silver dollar size. Does anybody have an idea what this could be? Do you think it could mess my tank up? It has been at their place for about 3 weeks and they do not know what it is either.

 

[vp39]

where they more blackish looking and shiny? If so it was methane gas bubbles.Yes that can hurt your tank if they pop. If they were not shiny then it could be just about anything and probably not bad.
Glenn

 

[rmor22]

Yes, they were more black and shiny.

 

[SteveP]

Valonia?

 

[Anonymous]

Valonia is what I was thinking too. Silver dollar sized is pretty big, though. I'm surprised the LFS didn't remove them. Then again, nothing the LFS does surprises me anymore.

 

[vp39]

My best guess is that it is methane bubbles. You need to get an emerald crab. They eat the methane. If it pops there is a good chance you will loose any fish in tank. I have seen the bubbles on many rocks and that is why the LFS didnt remove them, or they just figured more deco on rock. That who knows.
Glenn