Calcareous algae ID

[ShapeGSX]

This algae just started growing on this one rock one day. It is brittle, and it turns white from time to time, indicating to me that it is calcareous. Between the leaves of the algae are some clove polyps, which makes for a really nice rock.

It doesn't grow anywhere else in the tank. It doesn't spread to adjacent rocks. It just took over this one and seems content.

Any idea what it is?

 

[Janice12]

Looks like a species of Halimeda. Watch for it to grow more, it will look like a white small coin at the top of an old "leave." Not a bad species, and a good indicator of calcium levels, just like you thought!

 

[bluenassarius]

looks like udotea sp. to me

 

[mastou]

I would also say udotea...

/Magnus

 

[ShapeGSX]

The algae has grown a bit since I took that picture. Now that the leaves are larger, I'd have to agree with you. Udotea.

Really neat stuff. The algae grows and dies pretty quickly, and it leaves light and brittle calcium skeletons behind. They get blown around when I clean the rocks off.

 

[mastou]

I also had a bit some time ago, but it died rapidly after having produced some kind of spores/reproduction organs and never grew back...

/Magnus