White Coating on rocks

[michealprater]

I recently had a partial crash on my well established 40 breeder. I have been nursing it back to health with daily water changes and carbon. I am now getting a white coating all over the place. Since the crash my alk has been high, the calcium has been low and the mag swings all over the place. Could this be some form of precipitate?

 

[blaxsun]

Define "high" (your alkalinity, etc.)

 

[michealprater]

13ish DKH

 

[michealprater]

I would think dead coralline, but it’s corals that recently died. It’s soft and flaky and comes right off. I scraped a dead monti and it’s back today. It’s so strange in years of reef keeping I have never seen anything like this

 

[michealprater]

I have beat up the internet and cannot find anything that even resembles this