Halimeda Macroalgae. Picture taken February 2000
Nikon Coolpix 950 digital camera, no flash

Halimeda seems to sprout up out of the rocks years after you get it. This particular rock had been in my system for 2 years before this sprouted up.

Halimeda algae can quickly suck calcium out of the water because it is a calcareous macroalgae. This algae is not recommended for tanks without calcium reactors.

Halimeda Macroalgae. Picture taken July 2002
Nikon Coolpix 950 digital camera, no flash

I have halimeda growing all over the place it seems. I've been using it as a source of nutrient export which isn't ideal since it removes to much calcium from the system.