Blue Coralline Algae
Picture taken March 2002, Nikon Coolpix 950 digital camera, no flash

This is a really neat species of blue coralline which seems to be a slow grower and just about any other type of coralline will overgrow it. It only exists low in the tank near the sandbed level.

For a color comparison, typical purple coralline is to the left side and a lighter thicker purple coralline is to the right.  The blue is in center, the digital camera I used really had trouble representing the visual color seen with the eye.