Diatoms? Plz help ID.

[Pinkfrost001]

Tank is 4 months in.
Already had one cycle in tank and recently added a small CUC and 2 clowns.
I do weekly 20% water changes with my own RODI.
Cleaned tank yesterday and vacuumed sand in prep for water change this morning. Had a little bit of brown/red algae yesterday but it is much worse today even after the vacuuming. Not really on the rocks just the sand and light orange film on the glass of tank.

Is this diatoms again or something else?

current tank stats:
Ph 7.8
Phos .25ppm
Nitrate 0ppm
Calcium 400
dKH 9.5

thank you for any help

 

[JedClampett]

Yep looks like diatoms. Tank age checks out

 

[kingjames_dc5]

Your po4 is kinda on the high side. It sounds like diatoms to me as well. I would lower your po4 and should help some. If you get a tiger/strawberry conch it will definitely help keep the sand clean. And keep from having to vacuum on a regular basis. Also cutting back on light power or time will help as well.

 

[Reef.]

Looks like a mild case, I was going to suggest checking your rodi as it be releasing silicates which can cause diotoms,as you said it got worse after a water change but it looks a mild case so could just be a new tank thing.