Calcium consumption increasing, Alk staying the same.....Why?

clhardy5

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I have a 6 month old tank - that has a mixed variety of corals - not really heavily stocked yet, as I want the tank to be a little more 'stable'. But I do have 10 zoas, 3 hammers, 2 frogspawn, 2 torches, 6 various types of encrusting corals (raja rampage, space invaders), and a few stick sps. I use an Apex Dos and Trident to dos 2 part - and it's been keeping things pretty stable for the last couple of months. Alk was holding around 8.8, and Calc around 450. The apex was dosing about 25mls of alk, and until last Wednesday - about 10mls of Calcium per day to maintain these levels.

Then I noticed things started to change.....while alk is staying consistent, my calcium level dropped from 450 to 390 - over the past week. My trident has been adjusting the calcium dosage up in order to try to keep up, and as of today, it is dosing 40ml of calcium a day - and has only brought the tested level up to 415. At first I thought maybe it was a trident testing error - so I double checked with the Hanna. I know the level is still fine, but I'm wondering why would the tank be consuming more calcium at this time, and not also consume more alk? Is this an issue I should worry about - or is it the tank trying to figure things out, and I need to let it do its thing?

For reference:

Nitrate 10ppm
PO4 - .04ppm
Mag: 1390
Salinity - 34
temp 77
PH - 8.1

I have been using NoPox to bring down my nitrates - which it finally did -, and am now slowly ramping it down to find my maintenance dose. I also started dosing RedSea colors last week - after my ICP test came back showing low trace elements. And I use RedSeas AB+ (half dose) - every other day.
 
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clhardy5

clhardy5

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I suggest you read this article:


I also beleive that Ca test are more prone to inaccuracies.
Thanks. Interesting article...but I may have missed something - I didn't see where it talked about why the Calcium is being depleted faster than alk? I also understand that CA tests are prone to inaccuracies...but the decline is based on several tests....and two different tests - Hanna and Trident....and just for grins, I did an API calcium test and it registered low as well.
 

piranhaman00

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Thanks. Interesting article...but I may have missed something - I didn't see where it talked about why the Calcium is being depleted faster than alk? I also understand that CA tests are prone to inaccuracies...but the decline is based on several tests....and two different tests - Hanna and Trident....and just for grins, I did an API calcium test and it registered low as well.
What you are describing is impossible, it’s a testing error. Maybe your alk test is the error?
 

blasterman

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That tank by description isn't going to consume 60 points of calcium in a week. My heavily stocked SPS tanks maybe move calcium 60 points in a week. Testing was either wrong at the top end or bottom of the drift.
 
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clhardy5

clhardy5

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That tank by description isn't going to consume 60 points of calcium in a week. My heavily stocked SPS tanks maybe move calcium 60 points in a week. Testing was either wrong at the top end or bottom of the drift.
I think it may have been wrong at the top.....since both the Hanna and API show the current low value. I think I may replace the reagents, and recalibrate in a couple of days.
 

arking_mark

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Thanks. Interesting article...but I may have missed something - I didn't see where it talked about why the Calcium is being depleted faster than alk? I also understand that CA tests are prone to inaccuracies...but the decline is based on several tests....and two different tests - Hanna and Trident....and just for grins, I did an API calcium test and it registered low as well.

It was unclear from your dosing whether you were doing balanced dosing. If you were doing unbalanced dosing, it might explain the Ca drop.
 

Smarkow

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Have you noticed any precipitation? Calcium and alkaline molecules (most likely bicarb, but some debate) are depleted in a 1:1 ratio but are not usually measured in equivalent units and are not present in seawater at equal proportions (more alkaline molecules than Ca2+ ions). Magnesium levels can also affect uptake and precipitation. As can pH.

So if you are dosing unequally I think it is possible that precipitation events were caused, leading to swings in levels. Whether you adjust your dosing to Ca or Alk, I would make sure that the actual additions are in equal volumes and spread in small doses at separate times throughout the day.

Just my $0.02
 
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clhardy5

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It was unclear from your dosing whether you were doing balanced dosing. If you were doing unbalanced dosing, it might explain the Ca drop.
No....Not balanced dosing. The trident adjusts both independently based on testing (4 times a day for alk - and 2 times a day for calcium.
 
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Have you noticed any precipitation? Calcium and alkaline molecules (most likely bicarb, but some debate) are depleted in a 1:1 ratio but are not usually measured in equivalent units and are not present in seawater at equal proportions (more alkaline molecules than Ca2+ ions). Magnesium levels can also affect uptake and precipitation. As can pH.

So if you are dosing unequally I think it is possible that precipitation events were caused, leading to swings in levels. Whether you adjust your dosing to Ca or Alk, I would make sure that the actual additions are in equal volumes and spread in small doses at separate times throughout the day.

Just my $0.02
Thanks. I haven't noticed any precipitation. My PH has increased - now that the weather is nicer and we leave windows open more. It used to hang out at 7.9-8.0....and now stays around 8.1
 

arking_mark

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No....Not balanced dosing. The trident adjusts both independently based on testing (4 times a day for alk - and 2 times a day for calcium.

So just my 2cents, but Ca measurements are prone to inaccuracies and I wouldn't trust them for dosing.

7ppm Ca is 1dKH balanced.

Triton has a +/- 15ppm precision for Ca and a +/- 0.05 for Alk.

Since the tanks generally use Ca/Alk in a balanced or nearly balanced way, using Alk measurements to dose both Alk and Ca is much more accurate.

Let's use the extremes to provide some clarity.

Let's assume your actual tank parameters and target parameters are:
Alk = 8
Ca = 420

Your Triton reads low and measures 7.95 and 405 and you adjust each independently. You would end up with actual parameters of 8.05 dKH and 435 Ca. As your Triton gets out of calibration your Ca will suffer even more.

Had you just used the Alk measurement you would have just added 0.35ppm Ca and been at 420.35ppm.

So until there is a high-precision Ca tester, you are almost almost always better off using Alk measurements for dosing both Ca and Alk.

...and yes, over time,maybe several months or much more, will have to correct Ca if your tank doesn't consume it perfectly balanced.
 

Smarkow

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So just my 2cents, but Ca measurements are prone to inaccuracies and I wouldn't trust them for dosing.

7ppm Ca is 1dKH balanced.

Triton has a +/- 15ppm precision for Ca and a +/- 0.05 for Alk.

Since the tanks generally use Ca/Alk in a balanced or nearly balanced way, using Alk measurements to dose both Alk and Ca is much more accurate.

Let's use the extremes to provide some clarity.

Let's assume your actual tank parameters and target parameters are:
Alk = 8
Ca = 420

Your Triton reads low and measures 7.95 and 405 and you adjust each independently. You would end up with actual parameters of 8.05 dKH and 435 Ca. As your Triton gets out of calibration your Ca will suffer even more.

Had you just used the Alk measurement you would have just added 0.35ppm Ca and been at 420.35ppm.

So until there is a high-precision Ca tester, you are almost almost always better off using Alk measurements for dosing both Ca and Alk.

...and yes, over time,maybe several months or much more, will have to correct Ca if your tank doesn't consume it perfectly balanced.
I’m not certain your approximation of Ca/Alk equivalency is correct, it might just be an oversimplification or I may be missing something… but the concept you propose and your advice is solid. I agree that OP should follow this
 

Smarkow

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Thanks. I haven't noticed any precipitation. My PH has increased - now that the weather is nicer and we leave windows open more. It used to hang out at 7.9-8.0....and now stays around 8.1
Let’s assume your trident is measuring reasonably accurate… precipitation or consumption are the most common places for that Ca to go. Maybe your tank is more densely stocked than we realize? But if that were actually the case your alkalinity would likely be dropping.

If it really is accurate…

Did you add any sort of pH buffer to the tank, such as a borate containing product? This would not be used up by the corals or precipitated but would register on an alkalinity test.

Do you ICP?

I rarely recommend water changes, but in this instance a large water change which has been temperature, Alk, and pH matched should give some peace of mind.
 

Randy Holmes-Farley

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Thanks. Interesting article...but I may have missed something - I didn't see where it talked about why the Calcium is being depleted faster than alk? I also understand that CA tests are prone to inaccuracies...but the decline is based on several tests....and two different tests - Hanna and Trident....and just for grins, I did an API calcium test and it registered low as well.

Calcium is NEVER consumed without a balanced amount of alkalinity. That's why it was not mentioned.

The possibilities are:

1. Test measurement problems
2. You are adding alkalinity in some fashion without realizing it (this includes dosing nitrate or declining nitrate)
3. The calcium dosing solution is off
 
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clhardy5

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Calcium is NEVER consumed without a balanced amount of alkalinity. That's why it was not mentioned.

The possibilities are:

1. Test measurement problems
2. You are adding alkalinity in some fashion without realizing it (this includes dosing nitrate or declining nitrate)
3. The calcium dosing solution is off
Thanks.

1. Test measurement problems - I believe my trident may have been incorrect....I'm going to look into this further.
2. You are adding alkalinity in some fashion without realizing it (this includes dosing nitrate or declining nitrate) - Would the Nopox bringing the Nitrate down add extra alk?
3. The calcium dosing solution is off - Might be....I bought premixed from my LFS. I think I will mix my own from now on.


edited to ask better questions...
 
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clhardy5

clhardy5

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Let’s assume your trident is measuring reasonably accurate… precipitation or consumption are the most common places for that Ca to go. Maybe your tank is more densely stocked than we realize? But if that were actually the case your alkalinity would likely be dropping.

If it really is accurate…

Did you add any sort of pH buffer to the tank, such as a borate containing product? This would not be used up by the corals or precipitated but would register on an alkalinity test.

Do you ICP?

I rarely recommend water changes, but in this instance a large water change which has been temperature, Alk, and pH matched should give some peace of mind.
Thanks. I do not add any PH buffering to the tank, but do have a BRS CO2 scrubber and use the two little fishies media.

I did an ICP test two weeks ago, and it said my calcium level was 394.

Looks like I need to rethink letting the Trident control my calcium level :). I hear a loud and clear message that I should be dosing both calcium and alk in the same amounts. After my water change tomorrow, I'll retest with my Hanna kits, and make the necessary programming adjustments.
 

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Waboss

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I had high nitrates for a while (still a little high, but getting better). When I had high nitrates, I was having to dose more ALK to maintain the levels I wanted, as my nitrates came down, my ALK dosing requirements also came down (so now I'm doing more Cal than Alk). Based on what I'm seeing in my tank, I think it'll start balancing out to a more equal consumption/dosing requirement over time.

Incidentally, I started dosing TM's NP Bacto-balance to help with nutrient control, which is having a positive effect in reducing my nitrates.

Just thought my experience might be relevant to your concern.
 

adsf430

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Thanks. I haven't noticed any precipitation. My PH has increased - now that the weather is nicer and we leave windows open more. It used to hang out at 7.9-8.0....and now stays around 8.1
I've had the same issue. My my PH swings up, simply from keeping the windows open, my ALK drainsssss and nothing happens to CALC at all. And have to constantly adjust my dosing for it.
 
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