I agree, it's a good idea keep all the replies on this thread, it just makes it easier for members to help you if everything is in one place. R2R is very active, if you post, we'll see it
I also agree that this is almost certainly some kind of bacterial biofilm. I don't think it's anything to worry about, and I'd be surprise if it didn't just disappear on its own very soon. If it is bacterial, it could be consuming organics in the system, possible from the rock if it was real, wet live rock from a solid local fish store (and I hope it was!). Blow it off with your trusty turkey baster, and again in time I think it will no longer return.
I'll add, one month in and your tank should be cycled and ready for your first livestock. Do you have any questions about your cycle, and if your tank may be ready for livestock (assuming it was correctly cycled)? If so, we're all ears
Best of luck with your build!