Brown furryness on live rock

[Poseidon's snail]

Hi ,
I have a 55 litre all in one reef aquarium with live rock and live sand. And I run a skimmer and lots of biological media.I also have 2 filter pads supposedly cleaning the water before going in the skimmer.I have increasingly started to notice a white / brown furry substance on my rock.Does anyone know of this?
If so what can I do?

 

[Poseidon's snail]

Could anyone let me know how I can tune my Fluval PS1 skimmer to it's optimal skimming.

thanks

 

[Mastiffsrule]

Hello and #WelcometoR2R

The stuff on the rocks could be multiple things. It would be helpful if you could post some pics along with some info about your tank and current water parameters. A picture of how you have the skimmer set up may help also.