Sand discoloring

[supersmile]

Lately my sand has been turning like a mossy green color in some spots. I am not sure what is causing it. When I siphon it off it comes back nearly hours after. I changed my bulbs lately but I don't think that would cause it. Any ideas?

[tang daddy]

sounds like a bacteria strain similiar to cyano.

there is a post in reef that shows how to battle cyano check it out.