Phosphate Issue? Diatoms

[Kgramma]

I started my first saltwater tank around 5-6 months ago with dry rock and live sand. It was properly cycled and maintained. Never had an ammonia spike and keep nitrates 10 or lower. I have been struggling with diatoms since then (identified under microscope). I know it’s normal for a new tank but since I hit close to the 6 month mark I figured it had to be a phosphate or silicate issue. I’ll include a picture below but I’m guessing my phosphates are like 1-2ppm which seems like that might be the culprit. I just added chemi pure elite that has GFO. Do you think this will be helpful? Before I was only using the original chemi pure and purigen. I have a simple setup in a 32 gallon biocube. In tank media basket with filter floss, purigen and chemi pure. No skimmer.

 

[Gumbies R Us]

Are you doing water changes? If not I would start doing those