White hard tags

I know I need to add a photo and will do this week end - I did a search in this forum and could not find any thing close.

Here is a description:

On one of my LR I have 4 white long flat ridged growth of some sort - they don't move but one is starting to form a cup like formation (but flat) they are now about 1 cm long - they turn green during the day then when the lights turn off and first thing in the morning they are paper white again. They seem to be growing very slowly but are growing.

I will pop some photo's up this week end but just curious if this is familiar to anyone?

 

It's behavior sounds very much like Halimeda spp algae. It's a harmless calcareous macroalgae. Halimeda

 

Thanks for the link that could be it - I will post pics this week end. The only thing that make me wonder tho, is that it's both white and green - changing from light to dark. Could be the PH change???
Big thanks inwall

 

It will do that every night. It's calcareous (incorporates Calcium in it's tissue) and that's white. Every night, the chloroplasts (green things) migrate to the center for protection from predation leaving only the white Calcium skeleton. When the light comes back on, the chloroplasts come back to the surface.

 

Great info - that is it then
Thanks again