Hi,
I just started getting this in my tank. I am trying to figure out what it is and the best way to get rid of it and if their is a CUC crew that will get ride of it.
Looks like green hair algae. Looks like new rock. Looks like you have excess nutrients in your tank. If so you will need to decide how you want to deal with it. Me, I would start stirring the sand bed and cleaning the filters every week. Water changes also. Just what I would do. Good luck. And be patient.
We had a similar situation and did sand stirring, daily water changes for 5 days, daily sock changes for maybe 7 days. It finally got better but it was ugly for a month or so.