Do I have diatoms?

[Brian94558]

My 18g tank has been getting a gold/brown life coating on my send bad the past couple of weeks. I have one arc eye hawk, which I feed pellets every other day. I leave my halides on for only 5 hrs a day. The only filtration I have is a AC50 with purigen, chemi-pure, and filter floss. I also have a ball of cheato in a soup basket. My glass stays spotless but I've been noticing areas of hair algae popping up in a few spots along the rocks. For top off and water change I use RO/DI water from my lfs.

Here's a photo of what it looks like.
http://i264.photobucket.com/albums/ii162/audio101/P1020187.jpg

[mike_cmu04]

It is hard to tell for sure in the picture but it is either diatoms or cyano.

[Palting]

Golden brown is usually diatoms, though it's hard to tell from the pic. How long has the tank been up and running?

[KeMo]

looks abit more like cyano to me. As I had some that started kinda orange brown and then started to change to red. I Attacked it right away buy cutting back on feedings and sucking most of it out with my gravel vac. I also only ran my actinic lights as I read they feed off of the orange and red spectrum. In a week it was almost all gone.

[nvdiz]

looks like diatoms

[aleonn]

Looks like diatoms, but a more definitive answer would require additional pix or tank history.