ID on this green spot in my sand bed?

[jtt]

i have 2 of these little itty bitty green spots, and one purple one in my sand bed on the front of the glass. any ideas on what the heck it is?
12g nano
15 pounds live sand
21 pounds live rock
pH 8
ammonia 0
nitrites 0
nitrates 10-20

 

[jtt]

sorry for the screwed up pic. it shouldnt have uploaded like that... strange.... just turn your laptop on its right side.

 

[spanko]

Algae. Purple is Coralline, Green might also be or just some regular algae.