Diatoms or something worse?

[PoeLagoon]

I hate to be that "What's this?" guy but I wanted to confirm what I'm looking at here. Based on descriptions and images on the web, I believe it to be diatoms but wanted someone else’s opinion. My concern is that my NO3 and PO4 have both read 0 for months now so I concerned that it’s dinos. Currently it's only on the sand bed and it doesn't appear to be overly aggressive. Tanks is about 13 months old and I've already battled hair and cyano outbreaks.

 

[Impala67]

It looks like diatoms also green algae. My tank looked like that for a month all I had to do was reduce lighting and reduced feedings, it will pass.