Tank has been running just over a month, I had an outbreak of cyano which has turned brown then these have started to sprout up from the sand bed and on rock, almost looks like hair algae but not sure?
To me they look like tufts of hair algae. If you are able, pick it off with your fingers to manually remove. If you can't do that, try a toothbrush to scrub it off.
Ideally you would keep lights off while bacterial film grows on your rocks, about 2 more months. If you've already added photosynthetic creatures, consider reducing your lighting schedule and adding a cleanup crew that includes blue leg hermit crabs while your tank equalizes over the next few months.