massive calcium drop

[hgtuner08]

Im relative new to reefing and needed some advice regarding water chemistry and havent really been able to find my exact circumstances on other posts.  I have a tank that been going on a year now in March.  I have a trident setup and have calcium read every 12 hours.  About 3-4 months ago i started dosing soda ash I wasn't seeing any calcium uptake.  I was finally able to get my alkalinity dosing stabilized dosing 20 hours a day and pulling average DKH around 8.6 with 30 ml a day.  Overnight my calcium level went from 435 PPM to 380 PPM on a 100 gallon total water volume.  I had calibrated the trident a week or so before and also checked my calcium via hannah checkers and running trident test 2-3 extra times.  All the values are corresponding at around 380 PPM.

 

I guess my question comes in here why did I see a massive overnight drop in calcium and why wasn't my tank consuming any calcium before.  I wanted to move over to all for reef dosing.  Im going to stabilize my calcium by dosing calcium chloride and then move over to all for reef.  Is there an optimum time to dose calcium?  Right now I have my alk dosing 5 AM to 12 AM and have my calcium going 1-4.  Trying to slowly ease my calcium up to 420.  I added like 20-30 ML today during the day and have the auto dosing add 30 ML between 1-4 but I haven't seen the calcium go up at all.  I suppose this is from calcium being utilized as soon as its being added.  Any tips to calcium dosing?

[jhOU]

When daily dosing 2 part you should dose roughly* equal parts, and just base the dose on alk consumption. Daily calcium consumption can be hard to see when testing. When making parameter correction doses you will only dose what you are correcting. A sudden drop could be from precipitation. But you may want to verify your calcium with a standard titration test (red sea/salifert). I love my trident and hannah checkers, but those 2 are notoriously bad at calcium. I’d just recommend confirming calcium, make correction doses, and resume dosing at equal parts. 

[JJKK]

Yes.  Trident Calcium can rise or drop based on how much reagent is left.  I would think it is the Trident Calc measurement that is off.

[DaJMasta]

Otherwise, the only other way I know calcium drops suddenly is if it precipitates - and you'd likely see that in the tank or building up on the inside of plumbing.  Unlikely, I think, in both cases.