ID request - Brown bumps on rocks and sandbed

[itsacrispy]

Hi all,

I'm at work but will try to photograph this when I get home later tonight.

While I was cleaning the tank last night, I noticed colonies of light-brown bumps on the rocks and parts of the sandbed. Individually, they're about 1/16" in diameter and elliptical in shape. They don't appear individually though, rather as mats on top of snail shells, sand, rocks, walls, etc. I've even noticed them growing on dead parts of halimeda.

When I took a closer look, I also noticed that the mats are covered in a very fine hair. The hair never extends beyond an 1/8" long. The bumps do not move and they're quite difficult to remove from the walls. It takes at least 4 passes with a mag-float to remove them.

Does anyone know what these are? Since I see them growing on the dead halimeda, I'm afraid they might have a part in killing the macro algae off. I'd greatly appreciate any help!

Thanks!
Mike

 

[phishphood]

Diatoms?

 

[itsacrispy]

I thought diatoms came in the form of slimy brown mats, am I wrong?

 

[phishphood]

mmm...I think you're thinking of dinoflagellates?

 

[itsacrispy]

oooooooh. I didn't think of that. Thanks!

I'm guessing this is still part of the cylcing process then. I started w/ cyano, had some green hair, now diatoms. If I remember correctly, this is the last part of a "major" cycle.