Weird looking growth on live rock

[potatopuffer]

Hey everyone Ive been struggling to figure out what is growing on my live rock. I have a 150 gallon FOWLR with a 60-gallon sump that I've had for 2 years. I have a long spine porcupine puffer, red coris wrasse, harlequin Rusk, majestic angel, 5 lyretail anthias and a snowflake eel. My parameters are Temp - 77.6 PH - 8.4 Salinity -1.024 Nitate - 20ppm Phosphate - 0ppm Nitrite - 0ppm Ammonia- 0ppm Silica - 0ppm. I've been dealing with this for 7 months. At first I thought I had an algae bloom so I bought a GFO reactor and had no phosphates for the last 3 months. Then I thought it was silica causing an outbreak of diatoms. When I lightly brush the live rock a top layer comes off but under the top layer its stained to the rock. I'm running out of ideas of what it could be. Any thoughts?

 

[ShakeyGizzard]

first glance looks like an algae

 

[mpatterson42]

With the puffer and the harlequin what's your cleanup crew look like?

 

[potatopuffer]

With the puffer and the harlequin what's your cleanup crew look like?

I have a handful of hermit crabs and most of my snails died. I'm looking into getting turbo snails because they are larger.

 

[Tahoe61]

I would try Astraea Snails or an Urchin.

 

[potatopuffer]

I would try Astraea Snails or an Urchin.

Okay I'll give them a shot

 

[easycoral]

Organic is high. Strengthen your skimmer. Wash your socks every three days.