Yeah that's just brown algae. It appears on aquarium things, usually new things. Its actually diatom rather than an algae but as jdhef said, you can just wipe it off. Its most common on new plants, but can grow on decorations and other things too
I just had the brown algae (diatom) problem. They are still there just are obviously in decline. I just wipe them off during my once a week WC. Took a month or so maybe more, but obviously on decline now.