Gold substrate layer?

[Space]

I moved a 10 gallon set up to a 30. It's been up and running for about 3 weeks now, and has sand substrate.

The top layer of the substrate is this goldish/grey color that I never had in my smaller tanks.

Anyone know what this is, and if I should be worried about it? It seems like a lot to have built up in only three weeks if its just a detritus layer.

 

[Reygan2]

Probably diatoms. Very common in new setups. They are unsightly but will go away on their own in a few weeks. Can you post a pic?