What is this alage

[reefguitar]

I can't get the stuff to go away. When I stir the sand but it disappears but comes right back

 

[Diesel]

Diatom algae.

 

[Maritimer]

Diatoms are common in a new tank - and they look like what you posted.

(Welcome aboard, by the way!)

They tend to bloom for a few weeks or so, use up the available silica, and fade away - just in time for greener algaes to take over.

~Bruce