What is this on my sand?

[stharper2923]

What is this covering my sand? Did water change and vacuumed sand bed and it was back within 12 hours. It is also on glass and very hard to scrape off.

 

[dlsorensen]

Does it go away when you turn the lights off?

 

[stharper2923]

Oh not sure. We have Kessel APx90 lights so they are on cycle. I never watched. We did add coraline pink and purple algae kit 2 weeks ago. Could it be because of that?

 

[JZ199]

How old is your tank? It could be part of your "ugly stage" It looks like diatoms to me