what is this?

[troutman11111]

it looks like its pulling the rock together. a sponge?

 

[Fluff]

A sponge would be my guess as well. These ball sponges are really neat and can move but very slowly.

 

[GinaD]

I saw what the LFS called a 'sea sponge ball', but I think he was making up that name.

Your pic looks great. HOw big is this thing? To me, it looks like an inch in diameter.

 

[troutman11111]

about 1 in. it's these little things that always have me looking at the tank.