How do I get rid of diatoms?

[MamaLovesHerReefTank]

I have a 125 gallon tank that has been running for 3 1/2 years. We have been doing a 20 gallon water change weekly using rodi. We clean the glass and rocks weekly as well. We constantly have an issue with diatoms on the sand bed. We stir the sand weekly as well. How do I get rid of these diatoms. I honestly don't know my testing levels as I hardly ever test for anything anymore. I usually go by how my tank looks, corals are healthy, fish and inverts are all healthy. I did recently add some new dry clean rock about 3 weeks ago. Other than the new rock, there have been no changes. This has been going on for about 4 months. As soon as we stir the sand bed, within minutes the diatoms are taking hold again.
Thanks for any and all help.

 

[AZMSGT]

Doesn’t look like Diatoms. More than likely Cyano or Dinos

 

[Heart of Dixie]

Look at them under a microscope. If just on the substrate it could be diatoms or amphidinium dinoflagellates. Long & thin, diatoms. Roundish, dinoflagellates.

 

[NanoDJS]

stop doing water changes , check you rodi resin , your most likely saturated and leeching some silicates back into your rodi / you could use bakers yeast like a friggen pinch for that sized tank, like 1/60 th of a tsp , diatoms eat p / n / and silicates

 

[bacc2bacc]

Time and less light