Overnight Alk overdose!

It was a high concentration in a short amount of time in a certain spot that caused the precipitation. I use recipe 2 for that reason, it precipitates much less when dosed. IME, the change in pH is negligible. With your mag where it is, you should be able to maintain Ca and alk where you want, within reason.

 

Well after dosing alk and doing a 10 gal wc my alk sits around 11 and my ca around 350. Corals look pretty darn good considering the swings and the fish are great. Enough for today will continue to correct my ca back to 400 the next week.
Have to clean al my pumps tomorrow and the back wall from the calcium precipitate. My rocks and coralline algae have the thin white calcium haze though not sure how to approach that since it doesn't blow off. Will it smother and kill me coralline? Will it eventually dissolve back into the water?

 

It's mainly the pH spike from the large alk dose which causes the precipitation event (and therefore the drop of Ca). Calcium will continue to be prone to precipitation if you add more; you need to wait until the pH is stable (and at a lower value) again. Then dose your Ca back up.

 

Well this morning thigns have started to stabilize. CA is now at 380 and alk back down to around 10. My pH took a nice drop though and was only 7.74 this morning but is back up to around 8.08 this afternoon. Going to restart the alk dosing tonight ca dosing resumed this afternoon already. I guess I will just have to continue to test and keep an eye on things for awhile. Still have to clean my pumps thinking vinegar will do the trick.

 

I'm such a simple guy, who uses the KISS principle- maybe too much but-
this is yet another reason that thus far, I have no dosing pumps, etc.

Shoot, even my ATO (now only a 4g max if the in sump float sticks)
runs off no power, no selenoids, no electricity

Glad you seemed to have no livestock loss, and are fixing it rather easily