Orange Spots on Back Wall?

[Reefer37]

I can't get a decent picture of them for the life of me because you can really only see it with the blues on, but I've started noticing orange (almost looks rust colored) spots along the back wall of my tank.

Anybody have any idea what it could be or if anyone else has had this?

It's only on the black acrylic back wall of my display of my AIO.

 

[r20crazy]

do they move? if yes could be flatworms. could be coralline algae... comes in many colors

 

[Reefer37]

do they move? if yes could be flatworms. could be coralline algae... comes in many colors

Definitely not a flatworm or critter. It might honestly be coralline, I didn't know it came in orange.