Need an ID

[AZ_Reef]

Dino’s or diatoms? Need Purchased this used tank with rocks, corals, and fish about 2.5 months ago but sand is 2.5 month old. Brown stuff is only on sand and few small new rocks I put in two weeks ago. I do see some small bubbles on few places.

 

[reefpunk707]

Looks like diatoms to me

 

[muzikalmatt]

I agree it looks like diatoms. Does it go away when the lights are off? If so, that usually means dinos.

 

[AZ_Reef]

I agree it looks like diatoms. Does it go away when the lights are off? If so, that usually means dinos.

It does disappear at night and come back when light is on. I though diatoms disappear when light is off too? I Am going to take a look through microscope when it arrived.