Dosing Kh & Mg but not Ca

[Anthrax15]

Right now I am dosing 5ml of Kh every 2 days and am seeing a 30ppm lose of Mg over 8 days but Calcium has hovered at 430-420 testing almost daily. Is this normal to see or am I missing something? Im more so interested in the tank consuming that much Magnesium and not Calcium.

I am also dosing NO3/PO4 to keep my levels detectable. Tank is going on 4 months old, coralline algae growing and seeing growth on coral (Mixed reef).

Levels currently and what I am to keep them at:

Nitrates - 3-5ppm

Phosphates - 0.07-0.15

Alk - 8.5

CA - 420-440

MG - 1440

For testing, Im using:
Hanna - KH
Elos - Mg
Red Sea - Ca
Nyos - NO3
Hanna - PO4

 

[rmurken]

Did you have any water changes in the time period during which you were doing these tests? That could also be bolstering your Ca.

Also, don’t discount the imprecision of hobby test kits—even good ones. They’re all over the place, and a 30ppm difference in Mg could just be the test and not the underlying concentration. As long as your Mg isn’t too high or too low, don’t sweat it.

Same for Ca.

What are you using for Alk? 5ml every other day of a typical alk supplement probably isn’t much. So it stands to reason your Ca, which falls more slowly, isn’t going to be plummeting. Also, if you’re dosing a one-part supplement (a Ca acetate or formate based thing), then you’re doing both at once.

 

[Anthrax15]

Did you have any water changes in the time period during which you were doing these tests? That could also be bolstering your Ca.

Testing was done between water changes as to not effect results.

Also, don’t discount the imprecision of hobby test kits—even good ones. They’re all over the place, and a 30ppm difference in Mg could just be the test and not the underlying concentration. As long as your Mg isn’t too high or too low, don’t sweat it.

Same for Ca.

I have noticed a difference in Mg levels going from 1440 to 1410ppm. It just seems odd to me that my tank is consuming that much Mg but not Ca. Just wanted to make sure this is normal. Should I dose an equal ratio of Calcium to Alkalinity or is it fine to just dose Kh/Mg until the tank consumes more Ca?

What are you using for Alk? 5ml every other day of a typical alk supplement probably isn’t much. So it stands to reason your Ca, which falls more slowly, isn’t going to be plummeting. Also, if you’re dosing a one-part supplement (a Ca acetate or formate based thing), then you’re doing both at once.

Using BRS 2-part for dosing CA/KH/MG.

 

[rmurken]

Hobby test kits—even good ones—aren’t really precise. But they are designed to be reasonably accurate. The upshot being that the results for same or similar samples will all be in the right neighborhood, but don’t expect them to be exactly the same or track each other exactly.

So. I wouldn’t assume the 30ppm difference in Mg is all or even mostly actual consumption. Mg gets drawn down slowly. It’s more likely that the 30ppm drop is mostly noise than that something is consuming that much Mg.

I’d consider dosing the Ca part. If you’re consuming Alk, you basically have to be consuming Ca. Ca numbers move more quickly than Mg, but still far more slowly than Alk. So a week of tests between 420 and 440 without dosing doesn’t strike me as a reason not to dose it.

I don’t think you need to test Ca and Mg more than once a week (some don’t bother with Mg...I do it maybe monthly).

 

[Anthrax15]

Alright sounds good! If I am dosing 2.5ml of Alk per day to keep up with current demands, what would be the appropriate amount of Calcium to dose? Still trying to understand the ratio on how to dose.

At what point should I start dosing Magnesium? I would imagine 1400-1440 is a decent enough range to keep it within, should I add more MG when it drops below 1400?

 

[rmurken]

The two-part products are all designed to be dosed 1:1 by volume. So if 2.5ml/day alk, you would do 2.5ml/day Ca.

Different approaches on Mg dosing. I’d check what the BRS instructions are and just go with that. I think their Mg part is part chloride/part sulfate, which helps counteract the imbalance introduced by very heavy long-term dosing of the sodium-based Alk and Chloride-based Ca parts. As with everything, don’t try to do too much at once if you need to adjust.

Tbh, at your level of consumption I wouldn’t lose sleep over it—your water changes will mostly rub out any imbalance from the Ca/Alk dosing, and probably also keep your Mg where it needs to be. But you won’t go wrong dosing it according to their instructions (don’t recall then offhand).

 

[Randy Holmes-Farley Verified Community Expert]

Right now I am dosing 5ml of Kh every 2 days and am seeing a 30ppm lose of Mg over 8 days but Calcium has hovered at 430-420 testing almost daily. Is this normal to see or am I missing something? Im more so interested in the tank consuming that much Magnesium and not Calcium.

I am also dosing NO3/PO4 to keep my levels detectable. Tank is going on 4 months old, coralline algae growing and seeing growth on coral (Mixed reef).

Levels currently and what I am to keep them at:

Nitrates - 3-5ppm

Phosphates - 0.07-0.15

Alk - 8.5

CA - 420-440

MG - 1440

For testing, Im using:
Hanna - KH
Elos - Mg
Red Sea - Ca
Nyos - NO3
Hanna - PO4

There is no way for magnesium to decline without calcium declining about 10x faster, unless water changes are causing it.

 

[Randy Holmes-Farley Verified Community Expert]

Alright sounds good! If I am dosing 2.5ml of Alk per day to keep up with current demands, what would be the appropriate amount of Calcium to dose? Still trying to understand the ratio on how to dose.

At what point should I start dosing Magnesium? I would imagine 1400-1440 is a decent enough range to keep it within, should I add more MG when it drops below 1400?

i would dose the two/three part as directed (I designed it). Don't base the magnesium part on magnesium testing, unless it is getting too high already.

 

[Anthrax15]

Right now I am dosing 2.5ml per day to keep up with Alkalinity demands. What do you recommend dosage wise for Ca/Mg?

 

[Randy Holmes-Farley Verified Community Expert]

Right now I am dosing 2.5ml per day to keep up with Alkalinity demands. What do you recommend dosage wise for Ca/Mg?

It would help if we knew what exact product you are talking about.

 

[Anthrax15]

BRS for Kh/Mg/Ca. FishofHex for NO3/PO4

 

[Randy Holmes-Farley Verified Community Expert]

BRS for Kh/Mg/Ca. FishofHex for NO3/PO4

BRS sells two of my recipes, one using sodium carbonate and one using sodium bicarbonate. The latter is half as potent.

Do you know which?

 

[Anthrax15]

This is the exact order I purchased, though I opted for single pharma pouches instead of the larger bags.

2-Part Pharma Calcium & Alkalinity Bulk Total Package

Easily maintain calcium, alkalinity, & magnesium in your reef! The 2-Part Calcium & Alkalinity Total Package is the perfect answer if you want to make your own 2-part liquid dosing solutions and start dosing. Easily make single or multiple gallons of each solution at a time with the bulk...

www.bulkreefsupply.com

 

[Randy Holmes-Farley Verified Community Expert]

OK, you are using my Recipe #1. My recommendation is to dose the alk part to maintain alkalinity, to dose the calcium part at the same amount unless it is too low and needs a corrective boost or already too high (well over 500 ppm).

Also, dose the magnesium part not based on magnesium measurements, but at a rate of 610 mL of the magnesium part for each gallon of the alk part dosed. That can be once a gallon is done (less optimal), or more often, at a rate of 16% of the alk part (so 16 ml for each 100 ml of the alk part added).

The rationale for the recipe and more detailed directions are here:


An Improved Do-it-Yourself Two-Part Calcium and Alkalinity Supplement System by Randy Holmes-Farley - Reefkeeping.com

 

[Anthrax15]

OK, you are using my Recipe #1. My recommendation is to dose the alk part to maintain alkalinity, to dose the calcium part at the same amount unless it is too low and needs a corrective boost or already too high (well over 500 ppm).

Also, dose the magnesium part not based on magnesium measurements, but at a rate of 610 mL of the magnesium part for each gallon of the alk part dosed. That can be once a gallon is done (less optimal), or more often, at a rate of 16% of the alk part (so 16 ml for each 100 ml of the alk part added).

The rationale for the recipe and more detailed directions are here:


An Improved Do-it-Yourself Two-Part Calcium and Alkalinity Supplement System by Randy Holmes-Farley - Reefkeeping.com

So even though I am not seeing a movement of Calcium, still dose 2.5ml of Calcium daily as that is what I am dosing for Alkalinity?

Im having a hard time understanding how much I should dose for Magnesium based off what you stated. If I am dosing 2.5ml of Alk, what would that come out to be for Mg?

 

[Randy Holmes-Farley Verified Community Expert]

So even though I am not seeing a movement of Calcium, still dose 2.5ml of Calcium daily as that is what I am dosing for Alkalinity?

Im having a hard time understanding how much I should dose for Magnesium based off what you stated. If I am dosing 2.5ml of Alk, what would that come out to be for Mg?

Yes. Calcium moves much more slowly than alk, but the equal volumes take that into account. Only adjust if you see it trending too high or too low, not because it looks stable.

If you dose 2.5 ml per day of alk, then the magnesium amount would be 0.4 mL per day, but dosing a weeks worth (7 x 0.4 = 2.8 mL) or even a months worth (30 x 0.4 = 12 mL) all at once is fine. Definitely daily dosing is not needed for magneisum.

 

[Anthrax15]

Awesome! Thank you much, Randy! Would you account the 30ppm I am seeing in my testing to the quality of test kit and within an acceptable boundary?

 

[Randy Holmes-Farley Verified Community Expert]

If you mean the 30 ppm loss in magnesium, that may be test error, or a salinity difference between measurements. For magnesium, a change from sg = 1.025 to 1.026 is a change of ~50 ppm.

 

[Anthrax15]

@Randy Holmes-Farley I seem to be having a balancing act issue with NO3 and PO4. I can keep my NO3 stable at 5ppm all the way up to 12ppm via NYOS tester but my tank is either consuming a ton of PO4 or something is wrong. I am losing 0.10ppm per day of PO4 and I cannot seem to stabilize it. I am dosing 10ml of NO3 and 2.5ml of PO4 to keep my NO3 at 5ppm and my PO4 around 0.15ppm.

I am using FishofHex's NO3 and PO4 to dose. I appear to have Dino's and some slight green slime algae.