White velvet on rock?

[cliffhanger]

Hello
5 months age
65 gal
Skimmer asm
Chaeto in sump
2 lamps black box

Parameters are
No3 0.5
Po4 0.03
Alk 9dkh
Ph 8.2
Ca 420
Mag 1350
Sal 1025
Temp 26

Load fish 6 ... 4 small 2 medium size

All nights add 1/2 grams reef roids and 1.5 ml brigwell aminoacid And turn off 6h skimmer cup out

I got out biopellets 45 days ago
Any help[emoji848]

 

[cloak]

It looks like some type of fungus or possibly a bacterial mat. I had something similar in one of my tanks before, but it disappeared over time. As long as all of your inhabitants are doing ok then I wouldn't even worry about it. GL.