Randy Holmes-Farley
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A recent thread in the chemistry forum from someone who found that calcium increased with this product while maintaining alkalinity and using 1:1 dosing as advised by Seachem provoked me to check it's manufacturer specifications to see if it was a balanced additive.
From Seachem's claims about it, it is easy to see that it is not properly balanced, despite claims from Seachem that it is. For those who do not care to read further, it seems to have 15-25% too much calcium based on their specifications.
http://www.seachem.com/reef-fusion.php
"Most concentrated two part system; simple 1:1 ratio"
"Reef Fusion 1™ provides not only 100,000 mg/L of ionic calcium, but also includes biologically appropriate levels of magnesium, strontium, boron, iron, manganese, and molybdenum."
"Reef Fusion 2™ contains a mixture of carbonates and bicarbonates at an alkalinity of 4400 meq/L. "
Let's explore that.
Calcium is 100,000 mg/L. Calcium weighs 40 g/mole, so that is 2.50 moles/L.
The alkalinity is 4.4 equivalents/L.
To make calcium carbonate, each mole of calcium reacts with 2 moles of alkalinity. So 2.5 moles/L of calcium reacts with 5 moles/L (5 equivalents per L) of alkalinity.
In terms of making pure calcium carbonate, this product has excess calcium. Specifically, it has 13.6% too much calcium.
It is actually a bit tricky to know exactly how much calcium and alkalinity to have in a two part for two reasons (detailed below), but it is expected that the demand for calcium in a reef tank when using a two part is below the ratio needed for production of pure calcium carbonate due to replacement of some of the calcium demand by magnesium and strontium getting into the calcium carbonate crystal in place of calcium.
In my DIY two part (like from BRS), I chose to use slightly less calcium relative to alkalinity. My calcium part is intended to have 37,000 mg/L calcium (0.92 M) and the alk part has 1.9 eq/L alkalinity. Thus it is intended to have a slight excess of alkalinity relative to calcium. It may not be perfect, depending how the factors discussed below play out in any given reef tank, but it is in the right direction.
Note, the math discussion below is only for chemical/math nerds, and is really shown only so that folks do not throw out the criticism that I forgot these effects that impact the ratio of calcium to alkalinity needed in a reef tank:
1. Pure calcium carbonate does not form in reef aquaria. Magnesium and strontium get into the growing crystal of calcium carbonate, reducing the consumption of calcium relative to alkalinity. So even the "perfect" 1 mole of calcium for each 2 moles of alkalinity is a slight overestimate of the calcium required, and a perfect two part will require less calcium in relation to alkalinity by something like 12.5% (depending on exactly how much magnesium, especially, is getting incorporated, and that depends on exactly which organisms are present). I discuss that ratio in more detail here:
https://www.reef2reef.com/threads/r...g-three-parameters.321163/page-2#post-3981087
2. An even more esoteric effect relates to the salinity rise when using such a product from the sodium and chloride added. When the salinity is corrected back to normal, it reduces both calcium and alkalinity, requiring more dosing, but curiously, it doesn't require the same amount of each half to be dosed to offset this rise. I have calculated the salinity rise elsewhere,
http://reefkeeping.com/issues/2006-02/rhf/index.php
and it is on the order of a 32% rise in salinity after dosing 1.1 dKH per day for a year (both parts equally) for a total of 401.5 dKH (143.4 meq).
Let's take an example with a 100 liter tank, although tank size doesn't matter in this calculation. To add 401.5 dKH (143.4 meq/L) to 100 liters using the Seachem product with 4.4 eq/L (4,400 meq/L) takes 143.4 meq/L * 100 L /4,400 meq/L = 3.2 liters per year. At the end of that year, salinity has risen by about 32%.
Because of that salinity rise, when corrected back to normal, the alkalintiy decreases by 32%, so 9 dKH becomes 6.12 dKH, and requires extra additive to boost the alk back. That requires an extra 9-6.12 dKH = 2.88 dKH (1.03 meq/L) takes an additional 1.03 meq/l * 100 L / 4,400 meq/L = 0.023 L of alk additive. This effect is pretty small on top of the 3.2L added over that year, and corresponds to only an extra 0.7% of the additive.
The correction is not exactly the same for calcium. If we start at 420 ppm, a 32% drop brings calcium down to 286 ppm. To bring that back up by 420-286 = 134 ppm calcium takes 134 mg/L x 100 L / 100,000 mg/L = 0.13 L. That, in comparison to the ~3.2 L added over the year is a required correction of 4.1% of the total calcium added. So for calcium, this correction is not so trivially small, and tends to increase the amount of calcium needed.
From Seachem's claims about it, it is easy to see that it is not properly balanced, despite claims from Seachem that it is. For those who do not care to read further, it seems to have 15-25% too much calcium based on their specifications.
http://www.seachem.com/reef-fusion.php
"Most concentrated two part system; simple 1:1 ratio"
"Reef Fusion 1™ provides not only 100,000 mg/L of ionic calcium, but also includes biologically appropriate levels of magnesium, strontium, boron, iron, manganese, and molybdenum."
"Reef Fusion 2™ contains a mixture of carbonates and bicarbonates at an alkalinity of 4400 meq/L. "
Let's explore that.
Calcium is 100,000 mg/L. Calcium weighs 40 g/mole, so that is 2.50 moles/L.
The alkalinity is 4.4 equivalents/L.
To make calcium carbonate, each mole of calcium reacts with 2 moles of alkalinity. So 2.5 moles/L of calcium reacts with 5 moles/L (5 equivalents per L) of alkalinity.
In terms of making pure calcium carbonate, this product has excess calcium. Specifically, it has 13.6% too much calcium.
It is actually a bit tricky to know exactly how much calcium and alkalinity to have in a two part for two reasons (detailed below), but it is expected that the demand for calcium in a reef tank when using a two part is below the ratio needed for production of pure calcium carbonate due to replacement of some of the calcium demand by magnesium and strontium getting into the calcium carbonate crystal in place of calcium.
In my DIY two part (like from BRS), I chose to use slightly less calcium relative to alkalinity. My calcium part is intended to have 37,000 mg/L calcium (0.92 M) and the alk part has 1.9 eq/L alkalinity. Thus it is intended to have a slight excess of alkalinity relative to calcium. It may not be perfect, depending how the factors discussed below play out in any given reef tank, but it is in the right direction.
Note, the math discussion below is only for chemical/math nerds, and is really shown only so that folks do not throw out the criticism that I forgot these effects that impact the ratio of calcium to alkalinity needed in a reef tank:
1. Pure calcium carbonate does not form in reef aquaria. Magnesium and strontium get into the growing crystal of calcium carbonate, reducing the consumption of calcium relative to alkalinity. So even the "perfect" 1 mole of calcium for each 2 moles of alkalinity is a slight overestimate of the calcium required, and a perfect two part will require less calcium in relation to alkalinity by something like 12.5% (depending on exactly how much magnesium, especially, is getting incorporated, and that depends on exactly which organisms are present). I discuss that ratio in more detail here:
https://www.reef2reef.com/threads/r...g-three-parameters.321163/page-2#post-3981087
2. An even more esoteric effect relates to the salinity rise when using such a product from the sodium and chloride added. When the salinity is corrected back to normal, it reduces both calcium and alkalinity, requiring more dosing, but curiously, it doesn't require the same amount of each half to be dosed to offset this rise. I have calculated the salinity rise elsewhere,
http://reefkeeping.com/issues/2006-02/rhf/index.php
and it is on the order of a 32% rise in salinity after dosing 1.1 dKH per day for a year (both parts equally) for a total of 401.5 dKH (143.4 meq).
Let's take an example with a 100 liter tank, although tank size doesn't matter in this calculation. To add 401.5 dKH (143.4 meq/L) to 100 liters using the Seachem product with 4.4 eq/L (4,400 meq/L) takes 143.4 meq/L * 100 L /4,400 meq/L = 3.2 liters per year. At the end of that year, salinity has risen by about 32%.
Because of that salinity rise, when corrected back to normal, the alkalintiy decreases by 32%, so 9 dKH becomes 6.12 dKH, and requires extra additive to boost the alk back. That requires an extra 9-6.12 dKH = 2.88 dKH (1.03 meq/L) takes an additional 1.03 meq/l * 100 L / 4,400 meq/L = 0.023 L of alk additive. This effect is pretty small on top of the 3.2L added over that year, and corresponds to only an extra 0.7% of the additive.
The correction is not exactly the same for calcium. If we start at 420 ppm, a 32% drop brings calcium down to 286 ppm. To bring that back up by 420-286 = 134 ppm calcium takes 134 mg/L x 100 L / 100,000 mg/L = 0.13 L. That, in comparison to the ~3.2 L added over the year is a required correction of 4.1% of the total calcium added. So for calcium, this correction is not so trivially small, and tends to increase the amount of calcium needed.
Thanks for sharing this!
