Ca/Alkalinity help

[NeuroDoc]

I am having difficulty trying to figure out why I get the following parameters:

Ca 390
dkH 15
pH 8.4
Nitrate/Nitrite/NH4/Phos 0
Temp 80.8
spec grav 1.025

I know that my dkH is way too high, but I can't figure out why it got that high. I have a calcium reactor, using ARM aragonite media, but as I understand things, this should be putting Ca/CO3 into my aquarium in balance.

I use instant ocean salt mix, which tests to a Ca level of ~420, and a dkH of about 8.

Is it possible that my corals and clams are removing Ca disproportionately? What else might cause this to be so imbalanced?

I have turned off the Ca Reactor and will monitor levels and correct slowly with water changes. Should I consider adding CaCl? I've actually thought about bubbling some CO2 into my sump to bring down the pH a bit and use of the CO3 buffer. How dangerous would that be?

TIA for the help.

 

[DonW]

Have you verified those numbers. Usually IO has high alk, low ca and low mg. What is your Mg?

Don

 

[Boomer]

I agree with Don 100% there is something wrong with those numbers. A reactor with a pH and Alk that high is unheard of, unless it is from a new mix just added.. Your readings make no sense. Reactors rarely give a pH of 8.3. If your Alk rises 2.8 dKH there will be a rise in the Ca++ of 20 ppm or vise-versa.

How are you measuring those levels ? Who's kits ( dont' say Red Sea ) or meter ?

I've actually thought about bubbling some CO2 into my sump to bring down the pH a bit and use of the CO3 buffer. How dangerous would that be?

CO2 will drop the pH and have no effect on the Alk. A CO3 buffer will make things much worse. The pH will go higher and the Alk really high.

 

[NeuroDoc]

I am glad that these numbers make no sense to you either.

I am using Salifert test kits for the Ca, Alk, and Phos. The others are from a general saltwater test kit, and the pH correlates with my pH probe (that is now in my Ca reactor). I don't have a Mg test kit.

I will recheck the numbers tonight, including testing my replacement water (which I last tested months ago).

How often do the kits go bad?

 

[NaH2O]

When was the last time your pH probe was recalibrated?

 

[NeuroDoc]

Ok,

I retested. I don't know why I have those numbers written down from previous testing (of my IO mix water), but here's where I stand as of tonight at 1800 PDT:

Tank testing (Ca Reactor off for about 22 hours:
pH 8.4
Ca 400 (within standard error of test I would think)
dkH 13.1
Spec Grav 1.025
temp 81.2

My IO mixed fresh:
Ca 350
dkH 12.8
Spec Grav 1.025
temp 79

I apologize for those bad numbers in my post. Boomer is right, of course, and the IO mixes up with a relatively low Ca and high dkH.

It looks like my tank water is pretty close to what I mix up. So I guess my question is, should I be worried about these numbers? If I turn my Ca reactor back on and the dKH rises, how high is too high?

Nikki, the pH probe is new, only running about 2.5 weeks, and calibrated when initially put in system.

 

[NeuroDoc]

CO2 will drop the pH and have no effect on the Alk. A CO3 buffer will make things much worse. The pH will go higher and the Alk really high.

Is this because my kit tests for CO3, HCO3, and H2CO3?

 

[DonW]

Thats more like it. Look at the numbers and notice the tank is a little higher but by a balanced amount on each ca and alk. This would lead me to believe that first your reactor is turned up to high or is not needed. The numbers also lead me to believe that your not balancing you water changes by adding the needed ca only additive. Get yourself a Mg kit and I'm pretty sure you will find it low.
Hope this makes sense.

Don

 

[Boomer]

Again I agree with Don

 

[NeuroDoc]

So how much Ca should I be adding to my change water? Is there an additive that adds Ca and Mg?

 

[DonW]

So how much Ca should I be adding to my change water? Is there an additive that adds Ca and Mg?

I cant remember but there is a calculator here somewhere. I use three different additives as needed. Calcium chloride this time its esv. Kent Mg this time around. Esv alk part of the two part but I just keep it for emergencies unopened. These are just the ones I have now but I'm sure there are lots of other great additives. Once you get it down it will remain pretty much the same every time as long as your water change size doesnt change.

Don

 

[NeuroDoc]

Is this because my kit tests for CO3, HCO3, and H2CO3?

Based upon This article from Reef Keeping, it appears to me that test kits only measure CO3 and HCO3.

This article has been great, and links to a number of other articles that have helped my understand this chemistry.

 

[Boomer]

that test kits only measure CO3 and HCO3

Not really kinda. The kits measures all of the compents of Alk, of which most is CO3 and HCO3 but about 6-7% is borate.

Alk = [HCO3-] + 2[CO3--] + [B(OH)4-] + [OH-] + [Si(OH)3O-] + [MgOH+] + [HPO4--] + 2[PO4---] - [H+]

This will help you understand it more. It is very deep

What is Alkalinity
http://www.advancedaquarist.com/issues/feb2002/chemistry.htm

What Don was looking for, calculator

Reef chemicals calculator
http://home.comcast.net/~jdieck1/chem_calc3.html


So how much Ca should I be adding to my change water? Is there an additive that adds Ca and Mg?

You do not or should not raise the Ca++ more than 20 ppm / day and the Mg++ 100 ppm / day

You to choose additves for Ca ++ and Mg ++ and Alk Sup's

How to Select a Calcium and Alkalinity Supplementation Scheme
http://www.advancedaquarist.com/issues/feb2003/chem.htm

An Improved Do-it-Yourself Two-Part Calcium and Alkalinity Supplement System (also Magnesium)

Magnesium in Reef Aquaria
http://www.advancedaquarist.com/issues/oct2003/chem.htm
http://reefkeeping.com/issues/2006-02/rhf/index.php

Reef Aquarium Water Parameters (a summary general article)
http://www.reefkeeping.com/issues/2004-05/rhf/index.htm

There will be a quiz later

 

[NeuroDoc]

Boomer,

Thanks for the response. I think I now have an understanding of the chemistry involved. Now my questions are about actual practice.

According to the calculator you link to above, a balanced Ca and dkH, based upon the starting dkH of my freshly made saltwater, would require me to raise the Ca from 350 to ~450 before I even added it to my tank. Should I be doing this with my water changes? Won't I have to worry about precipitation (in my bucket)?

I also need to check the Mg in my tank and my change water. I will aim for a level of 1300-1350 ppm. If I need to add to my new water, is there anything about epsom salts that should concern me? If not, I will use the calculator to figure it out for the volume of my change water.

I can correct the Ca level in my tank, but I should do so slowly, no more that 20-25ppm/day. Once my tank is "in balance" should I expect to see both levels drop in balance? (I have some clams, lps, and sps in my tank) If so, then I should be able to set my Ca-reactor to run at an appropriate rate to keep my levels stable. How should I expect to see the Mg level drop? i.e. Is Mg taken up by organisms to any great extent, or is it just lost by water changes/precipitation? (never mind, found the answer in Reef Aquarium Water Parameters by Randy Holmes-Farley in ReefKeeping Magazine. I guess I'll need to figure out how much Mg my Ca-reactor is adding to the tank, if any.

Thank you for all your help. I'm ready for your quiz.

 

[DonW]

If you correct the water changes you shouldnt need to do anything to the tank itself after you get it balanced. The carx will take care of it for you. Mg is the only thing that may need help depending on the carx media.

Don

 

[Boomer]

Neuro

According to the calculator you link to above, a balanced Ca and dkH, based upon the starting dkH of my freshly made saltwater, would require me to raise the Ca from 350 to ~450 before I even added it to my tank. Should I be doing this with my water changes? Won't I have to worry about precipitation (in my bucket)?

Yes that is corrct. No, you should not be getting a precip, just dont' dump in all the Ca++ sup (Kenty turbo cacium for example ) at once.


also need to check the Mg in my tank and my change water. I will aim for a level of 1300-1350 ppm

Yup about that, and when you bump it up do not be adding Ca++ at the same time. And 100 ppm at a time for Mg++.


I can correct the Ca level in my tank, but I should do so slowly, no more that 20-25ppm/day

Yes

Once my tank is "in balance" should I expect to see both levels drop in balance?

No, the Alk will always drop faster than the Ca++, as the Alk is also used to neutalize acids and such things. A normal balanced drop is for every 20ppm Ca++ lost there will an equal 1meq/ l / 2.8dKH loss in Alk but your Alk could end up droping twice that do to its need in other reactions.


If so, then I should be able to set my Ca-reactor to run at an appropriate rate to keep my levels stable

A Calcium reactor is not a cure-all. You may need to still sup the tank with things like kalk. Many with reactors are still sup'ing therir tanks, usually to correct for pH or the calium output of the reactor is not enough for their tank demands.

Mg taken up by organisms to any great extent

It is taken up to some extent but no where near as much as Ca++

Ok your last reading assignment for now

A Simplified Guide to the Relationship Between Calcium, Alkalinity, Magnesium and pH
http://reefkeeping.com/issues/2006-06/rhf/index.php

When Do Calcium and Alkalinity Demand Not Exactly Balance?
http://reefkeeping.com/issues/2004-12/rhf/index.htm

 

[NeuroDoc]

Thank you again, Boomer.

My Ca reactor has been off now for the past three days. Do these numbers make any sense? They are taken 48 hours apart.

9/1@2000

Ca 400
dkH 13.1
pH 8.2

9/3@2000
Ca 350
dkH 9.6
pH 8.2

By my calcuations, for that drop in dkH the Ca should have only dropped by 25ppm. Is that correct?

More likely, my 400ppm is incorrect, seeing how the dkH fell from Thurs (8/31) to Fri (9/1). Then the drop from 390 to 350 from Thurs to Sun with the drop in dkH from 15 to 9.6 would make sense to me.

 

[Boomer]

If we went only by Ca++ dropping 40 ppm, from 390 to 350, then the Alk would/should drop 5.6 dkH. And 13.1 - 5.6 = 7.5 dKH, which it should be around if the Ca++ dropped 40 ppm but you are at 9.6... red flag

If we went only by Alk dropping from 13.1 to 9.6 then the Ca++ drop should have been 25 ppm and not 40 ppm. red flag.


The only thing that would make any sense is if the Ca++ was say 400 and dropped to 375 ppm or if you want 390 to 365. Or if the Alk dropped more than the kit shows and is more like 7.5 dKH. It looks like some kind of testing error or bad kit.


If the Ca++ dropped 40 ppm it would make sense if the Alk went to 7.5 or even lower and not know 9.6 dKH. It does not make sense at all to loose that much more Ca++ than Alk. Here you are loosing more Ca++ than Alk, lots more and that can't happen. Something is wrong.

 

[NeuroDoc]

If we went only by Ca++ dropping 40 ppm, from 390 to 350, then the Alk would/should drop 5.6 dkH. And 13.1 - 5.6 = 7.5 dKH, which it should be around if the Ca++ dropped 40 ppm but you are at 9.6... red flag

I should have restated the numbers from Thursday (my very first post):

8/31 @2000

Ca 390
dkH 15

So the 5.6 drop in dkH (from 15; corresponding to the 40ppm drop in Ca) would put me at 9.4 last night, which is pretty close to the 9.6 I measured. That is why I think my Ca measurement from Friday (400ppm) was screwed up.

I will be getting a test kit for Mg today (if my LFS has one in stock), and I'll post those numbers. I did add some Ca supplement to my tank last night, aiming for a 25ppm increase. I will retest tonight at 2000 and post the numbers.

 

[DonW]

You'll get it. Just dont try to get it exact, this usually leads to unnecessary dosing and swings.

Don