Signs of Cyano? (Pic)

[badfish]

I noticed that my sand bed has been getting neon green and purple underneath the sand, where it meets the glass. The top of the sand is perfectly clean. See pic below, is this a sign of cyano starting, or is it just my tank maturing. Tank has been up for close to six months, i do weekly water changes (10%) with RO water from Walmart (purple cap). I did intial fill up with tap, but thats the only tap that has touched the tank, and had phosphates checked 1-2 months after initial fill, and they were indetectable.

Pic
http://im1.shutterfly.com/procserv/47b5d935b3127cce928639b0dd7900000016108AaOGjdi4Ztq

Thanks,

Jeff

 

[fishfreek]

this is not a sign of canyo. The green is algae more than likly and the purple could be coraline if its growing in circular patterns.

 

[badfish]

its more of a discoloration in the sand, did you see the link to the pic? I am starting to grow coraline on my powerheads and on back wall, and it is in a circular pattern. What i am talking about is actuall the coloration of the sand, i think. Its not on the top of the sand, but underneath maybe a half an inch.

 

[badfish]

can coraline alage grow on glass underneath the sand?

 

[fishfreek]

Yes and yes I saw the link and looked at it. Canyo goes on the surface of the sand not betweent the sand and glass. The areas where the green and purple is not totally void of light. Some lighting from the tank lights gets down in there thru the glass itself.

 

[malkore]

If any cyano forms between the sand and the glass, it won't go more than 1/8" down. Cyano is aerobic...it needs oxygen, so it can't live very far into the sand at all.

 

[badfish]

Thanks guys.