Alk Crash - Advice, please.

[>>klong<<]

I went away for 4 days and noticed that my purple stylo was almost completely dead when I got home. I tested my parameters and notice that my alkalinity was at 6.9 (Hanna) - I typically run about 9.1-9.3. I looked at my dosing pump and saw that the output of the line was completely solid with precipitate. I dose All for Reef with a Kamoer pump. A couple questions:

Could this cause the stylo to completely bleach out in 4 days? No other corals seem to be doing that bad. I have a couple other easy SPS (monti) that don't seem to be hurting.
How quickly can I bring my alkalinity back up? I think ppl typically recommend a max of 1dkh/day.
How do I keep this from happening again? Maybe cutting the dosing tube outlet at an angle?

In case it's valuable, here are the rest of the parameters I tested:

pH 8.4
NO3: 0.0 <- I've been struggling to keep my nutrients stable recently, too. NO3 is always low, PO4 is always high.
PO4: 0.12
Ca: 410

 

[IslandLifeReef]

I went away for 4 days and noticed that my purple stylo was almost completely dead when I got home. I tested my parameters and notice that my alkalinity was at 6.9 (Hanna) - I typically run about 9.1-9.3. I looked at my dosing pump and saw that the output of the line was completely solid with precipitate. I dose All for Reef with a Kamoer pump. A couple questions:

Could this cause the stylo to completely bleach out in 4 days? No other corals seem to be doing that bad. I have a couple other easy SPS (monti) that don't seem to be hurting.
How quickly can I bring my alkalinity back up? I think ppl typically recommend a max of 1dkh/day.
How do I keep this from happening again? Maybe cutting the dosing tube outlet at an angle?

In case it's valuable, here are the rest of the parameters I tested:

pH 8.4
NO3: 0.0 <- I've been struggling to keep my nutrients stable recently, too. NO3 is always low, PO4 is always high.
PO4: 0.12
Ca: 410

A swing like that could possibly be a cause, but I doubt it, especially since no other coral seems affected. The swing might have been the last straw for that coral. Don't give up on it though, it may come back if there is any flesh.

I would try to bring it back up over a couple of days. One dKh a day seems fine to me.

 

[Nigel35]

have your nutrients changed dramatically? I've seen when their is a sudden, steep imbalance of nutrients this kind of bleaching can occur. I had a beautiful Bali slimer acro colony bleach in 3 days due to this form of necrosis.