Dosing almost 2x Calcium vs. Alk?

[MyOtherCarIsAFishtank]

Help! I started 2 part dosing 2 weeks ago. I have about 120 gallons of water volume and numerous frags (50+) plus normal colonies. Tank is heavy SPS and LPS, but has many softies too. Nothing is huge, but many colonies are medium size plus all the frags. I started 2 part autodosing because my life got crazy and I fell behind in manual dosing, so my numbers got low.

I use BRS 2 part via 2 BRS dosing pumps. I am using 2x the calcium addition now compared to Alk. I test with a Hanna Alk meter and API Calcium test kit. A recent Triton testing seems to show my test kits are working. Here are some recent readings from once I got Alk and Calc up some (still working on Mg).

7/29 Mg 1100 Ca 340 Alk 8.2
(Adjusted Calc dose after test to slightly higher ml/day, and dosed Mg)

7/30 Mg 1200 Ca 360 Alk 7.84
(Dosed Mg)

8/3 Mg 1200 Ca 320 Alk (9.2)
(Dosed Mg and upped Ca per day and decreased Alk per day)

My Ca per day has ranged from 57 mL/day to now 90. Alk started at 57 too, but now is down to 40 mL/day. Any ideas why Alk is going up but Calc is still going down? Added a few gallons of salt water recently to replace some I used in a dip vat for new frags, but no other water changes lately aside from normal ATO RO/DI.

 

[Diesel]

If your test results are somewhat accurate you should pay attention to how much you dose just get your parameters to the target level.
Just you know if the CAL is low like in your case and you raise it automatically your ALK will drop some.
It can be a pain to get dialed and it takes time to.
I remember when I was dosing I dosed over 300ml ever day on alk and cal on a 200g

 

[Billdogg]

I would recheck your Mg. I suspect that it is running a bit low. Aim for 1350 as your target number. As long as Mg is low, you will never be able to bring Ca and Alk into equilibrium.

 

[460Mag]

Make sure your dosers are working correctly and putting out what you expect. Ive had more than one problem with those brs dosers. Make sure there is no air bubbles in the lines.

 

[Randy Holmes-Farley Verified Community Expert]

I would recheck your Mg. I suspect that it is running a bit low. Aim for 1350 as your target number. As long as Mg is low, you will never be able to bring Ca and Alk into equilibrium.

Whether it is low or high or anything, magnesium cannot ever cause more calcium to be used than the proportion amount of alkalinity.

 

[Randy Holmes-Farley Verified Community Expert]

Unless you are providing alkalinity some other way, the actual usage of calcium is not more than the proportional amount of alkalinity.

In this case, the dosers may be delivering different amounts than you think (very common, you can't go just by time), or water changes with a low calcium mix (like norna IO) cause more need for calcium.

If nitrate is declining a lot, that can boost alkalinity.

 

[MyOtherCarIsAFishtank]

Thanks all. The usage I see in the dosing containers matches (approximately) what my APEX is set to deliver. I am using Reef Crystals salt mix. I am going to test the dosing liquid directly by adding small amounts to a test solution. Maybe the problem is in my mixing, etc.

 

[Clownfishy]

@MyOtherCarIsAFishtank I have been having a similar issues, see here. I was thinking that the calcium I made up was loosing its potency over time, although I am not sure the science behind this or if this is even possible! I got to the point where I was dosing 30ml of Soda Ash and 75ml Calcium Chloride per day! Yesterday I made up a fresh batch of Calcium Chloride and dropped my dosage back down to 30ml of each during the last 24 hours. Too early to say but previously, I would have seen my Calcium start dropping right away but it hasn't. I am going to add another 15ml of Calcium Chloride today to see if that brings my Calcium back up and more importantly, holds there. As you can see, my Alkalinity is rock solid. I will let you know how it goes.
How old is the batch of Calcium Chloride you are using?