ID please - Cyano or Diatom

Thats right. I have googled images for cyano & diatoms on sand, for me they both look similiar. I wish its only diatom otherwise I have some big problem

 

I am having the same issue although my tank has only been setup for around 6 weeks with no fish, inverts or corals in it yet.
Seems like when I turned my lights on again after a week or so with them off, more of the rusty brown algae formed on the sand. It looks really nasty and took away my nice looking white sand.

 

Thanks everyone who helped on this !! all diatoms gone now and i have sparkling white sand again..so whoever gets diatoms, just wait for 2 weeks before you try anything.

 

Glad to hear! Usually diatoms are pretty easy to deal with. Glad to hear it turned out to be diatoms.

 

Glad they are gone. They do usually take 2-4 weeks to eat up all the silicates lol. Also depends on the CuC lol.

 

FYI- if you are not using RODI water for water changes you can get little blooms of diatoms after partial water changes. This is due to the phosphates/silica typically found in most tap water.