what is this

[MERCTECH]

i woke up this morning and one of my live rock is developing some brown fuzzy stuff on the highest point of the rock. i am one month and one day in. i known that i am due for a water change....will be doing this this weekend

 

[Feron]

sounds like your diatoms (algae phase associated with the near end of your cycle) are a bloomin.
They should burn themselves out once they consume the phosphates in your water.

(Well, that's my take on it, I assume it's a new setup)