I had something similar to that happen to me after I set up my new tank. Only I have to say mine was pretty bad. I couldn't see the wall from the side view of the tank, and we have striped wallpaper! I wondered if it was bubbles or bacteria or sand that I didn't get rinsed well. I turned off the filter and waited for everything to settle for a bit. If it rose it was air, if it sank it was sand, and if it swam in circles I frowned a bit.
Fast forward about 1.5 - 2 weeks... Must have been a bloom, cleared right up. And my mopani that I added all got fuzzed over. They looked like they were covered in 1/4" of cotton for a bit. The brigs snails however, and the SAE took care of that in no time. I think they appriciated it actually.
(yes, fish in cycle, live plants, bi weekly 50% wc's, everyone lived, painfully slow stocking at the time, happy healthy cycled tank now. Seems I'm always swimming against the flow)