Montipora Snow?

[Hayden Henry]

Hi all! A couple days ago I did a sizeable water change on my tank to help remove Cyanobacteria, and all was normal in the tank was normal for a day, but yesterday evening I noticed what looked like snow on my montipora?

It was not there in the morning and nothing has been introduced to the tank for several weeks. Nitrates are near zero and nitrites are at zero, phosphates are low and I maintain dKH around 10.

Any idea what this is or how I could fix it?

 

[Irregardless]

Mine looks like this when its growing quickly. I wish i had more insight as I am unsure why.

 

[anthonymckay]

dkH at 10, but near zero nitrates and phosphates, that's asking for trouble with sps.