Diatoms? Something else? Any help on how to get rid of.

[Mattdavid121]

Here are some pictures, been googling, have seen it before. I think it’s diatoms, but not sure.
water parameters:
Nitrates: 5ppm
Alk: 8.3
Phosphates: 0.02
Calcium: 450
Magnesium: 1430
Salinity: 1.026

 

[vetteguy53081]

Detrious and a bunch of pinapple sponges. Nothing to take tank down but I would use the edge of a credit card and scrape then siphon away.
Clean filters thereafter.
What filtration are you using ?

 

[Mattdavid121]

I have a sump under my Red Sea 350. Two filter socks and a Nyos protein skimmer with an algae scrubber.