How a Two Part Alkalinity and Calcium System Works, and Why it Matters

[Randy Holmes-Farley]

Hi Randy, i've read your article about improve alk dosing by heating up NaHCo3, in our country they provide 2 products that is NaHCO3 and Na2Co3, can i choose Na2Co3 instead of heating up NaHCO3 like you said ? And if possible, what is the dose ? Thank you !

If it is suitably pure, sodium carbonate (Na2CO3) is just fine. The only reason for the baking in my recipe is that food grade baking soda is cheap and readily available while Na2CO3 in food grade is harder to get (or at least was when I designed the recipe).

The recipe using 594 grams of sodium bicarbonate, converts to 375 grams of Na2CO3 when fully baked. So use 375 grams.

 

[Waldek M.]

Whether dosing calcium chloride in larger amounts than NaOH and salt without NaCl (these are equal) may affect the ionic balance?

 

[Randy Holmes-Farley]

Whether dosing calcium chloride in larger amounts than NaOH and salt without NaCl (these are equal) may affect the ionic balance?

Yes, but generally the only time there can be a large deviation from 1:1 for extended time periods is when absolute dosed amounts are low, and hence any imbalance is small.

Can you describe your dosing in more detail?

 

[Waldek M.]

Yes, but generally the only time there can be a large deviation from 1:1 for extended time periods is when absolute dosed amounts are low, and hence any imbalance is small.

Can you describe your dosing in more detail?

I don't have a big demand and I give 20 ml of NaOH (40 g/l), anhydrous calcium chloride 29 ml (55.5 g/l) and salt without NaCl in the same amount as NaOH. Such doses allow me to maintain levels of 8dkh and 410 Ca. I make water for water changes using TM Pro Reef salt, which has similar parameters. Should I still add salt without NaCl in the same amount as NaOH?

 

[Slark]

If it is suitably pure, sodium carbonate (Na2CO3) is just fine. The only reason for the baking in my recipe is that food grade baking soda is cheap and readily available while Na2CO3 in food grade is harder to get (or at least was when I designed the recipe).

The recipe using 594 grams of sodium bicarbonate, converts to 375 grams of Na2CO3 when fully baked. So use 375 grams.

Thank you Randy, one more question, i do water change 1% daily like you said, i have a 900 litres tank and i change 10l every evening and i follow dosing alk, ca, mg like your article for few months. The thing here is my salinity getting high everyday, previously it was 1025 and now it 1027. I use less salt per 10 litres per day and add more fresh RODI water but it still the same. Can you give me some advice ?

 

[Randy Holmes-Farley]

I don't have a big demand and I give 20 ml of NaOH (40 g/l), anhydrous calcium chloride 29 ml (55.5 g/l) and salt without NaCl in the same amount as NaOH. Such doses allow me to maintain levels of 8dkh and 410 Ca. I make water for water changes using TM Pro Reef salt, which has similar parameters. Should I still add salt without NaCl in the same amount as NaOH?

What size aquarium?

 

[Waldek M.]

What size aquarium?

about 350 liters of water alone

 

[Randy Holmes-Farley]

Thank you Randy, one more question, i do water change 1% daily like you said, i have a 900 litres tank and i change 10l every evening and i follow dosing alk, ca, mg like your article for few months. The thing here is my salinity getting high everyday, previously it was 1025 and now it 1027. I use less salt per 10 litres per day and add more fresh RODI water but it still the same. Can you give me some advice ?

That range is ok, but to keep it from getting higher, I’d just adjust the salt in the new water downward until the salinity is stable. The two part has more “salt” in it than seawater, so the amount of salt that accumulates can be substantial.

 

[Randy Holmes-Farley]

about 350 liters of water alone

That’s effectively a very low dose, so I would not worry about it.

I’d also say that the difference between 1:1 and what you are dosing is almost insignificant.

9 extra mL of 55.5 g/l calcium chloride = 0.5 g calcium chloride. Put that into 350 liters and it only boosts calcium 0.18 ppm per day. Even after a month of that dosing it would be hard to detect that extra 5 ppm reliably.

 

[Waldek M.]

That’s effectively a very low dose, so I would not worry about it.

I’d also say that the difference between 1:1 and what you are dosing is almost insignificant.

9 extra mL of 55.5 g/l calcium chloride = 0.5 g calcium chloride. Put that into 350 liters and it only boosts calcium 0.18 ppm per day. Even after a month of that dosing it would be hard to detect that extra 5 ppm reliably.

Thank you for your comprehensive answer

 

[Randy Holmes-Farley]

Thank you for your comprehensive answer

You’re welcome. Happy reefing.

 

[Randy Holmes-Farley]

I think I made a math mistake, but the difference is still only 0.5 ppm per day and I’d say to ignore any concern about not being 1:1. Stick with what you are doing.

 

[Waldek M.]

I think I made a math mistake, but the difference is still only 0.5 ppm per day and I’d say to ignore any concern about not being 1:1. Stick with what you are doing.

Ok.thanks

 

[kilnakorr]

I must confess I find this article a bit hard to understand, even after reading it a third time.

The ion imbalance is the Sodium and Chloride values, that can be skewed over time depending on the compounds we add for alk. and Ca. correct?

2. A second method involves using a third part intended to correct these ion imbalances. This method is technically simpler than #1 since one is not deciding what can go where.

Commercial approaches in this regard include Tropic Marin Balling Part C and Aquaforest Reef Mineral Salt as the third part.

I can't understand how any of these NaCl free salts can correct this imbalance. Can you elaborate?

 

[Randy Holmes-Farley]

I can't understand how any of these NaCl free salts can correct this imbalance. Can you elaborate?

Sure.

If sodium chloride is accumulating due to using calcium chloride and sodium (bicarbonate/carbonate/hydroxide) then one needs to fix it.

Sodium chloride is normally by far the biggest component of a salt mix.

If you leave it out, you have a salt mix without sodium chloride.

If you add that mix to seawater that has an excess of sodium chloride, then that excess disappears and you are left with all ions at normal ratios, albeit at slightly elevated salinity.

When you lower the salinity back to normal, you are left with a normal salt mix at normal salinity.

Does that make sense?

 

[SewerynAquaforest]

Hello Randy , great article. Thank You. Could You please send me a PM ? It seems that You don't receive messages. I would like to clarify something to this article. Thank You.
https://aquaforest.eu/en/guides/reef-mineral-salt/

 

[kilnakorr]

Sure.

If sodium chloride is accumulating due to using calcium chloride and sodium (bicarbonate/carbonate/hydroxide) then one needs to fix it.

Sodium chloride is normally by far the biggest component of a salt mix.

If you leave it out, you have a salt mix without sodium chloride.

If you add that mix to seawater that has an excess of sodium chloride, then that excess disappears and you are left with all ions at normal ratios, albeit at slightly elevated salinity.

When you lower the salinity back to normal, you are left with a normal salt mix at normal salinity.

Does that make sense?

Yes, that makes perfect sense.
I might not have been very clear in my question.

In think the term 'ion imbalance' is unclear to me. What ions are we talking about, and how do they become unbalanced?
It might be the English words, that gives me a hard time understanding this, as I can't seem to picture the reactions that could happen.

Adding calcium chloride in vast amounts would obviously raise the calcium levels and chloride levels. How can this impact salinity?
As the calcium is consumed by corals, chloride would remain, and creating a sodium/chloride imbalance?
Are the above scenarios what the artcle is about?

I'll go read again...XD

 

[Randy Holmes-Farley]

Yes, that makes perfect sense.
I might not have been very clear in my question.

In think the term 'ion imbalance' is unclear to me. What ions are we talking about, and how do they become unbalanced?
It might be the English words, that gives me a hard time understanding this, as I can't seem to picture the reactions that could happen.

Adding calcium chloride in vast amounts would obviously raise the calcium levels and chloride levels. How can this impact salinity?
As the calcium is consumed by corals, chloride would remain, and creating a sodium/chloride imbalance?
Are the above scenarios what the artcle is about?

I'll go read again...XD

We are talking, for example, about potassium (and every other ions except sodium or chloride).

This is the pertinent section:

Accumulating Sodium and Chloride

A very important consequence of using a two part is that sodium and chloride are added with every dose. Over time, this effect is quite significant. The actual salinity increase will vary based on exactly what other ingredients are incorporated into the two part, and in what form, but we can estimate the minimum effect one would see without water changes from just the alkalinity and calcium additions.

Assumption: add 1 dKH of alkalinity and the balanced amount of 7 ppm calcium each day. 1 dKH of alkalinity causes 0.36 meq/L of sodium to accumulate, or 8 mg/L sodium. The calcium chloride addition will add 12.4 ppm of chloride. Importantly, the Na to Cl ratio is exactly that found in NaCl, and we will come back to that later. We are thus adding 8 + 12.4 mg/l every day, or 632 mg/L in a month = 0.63 ppt each month =7.5 ppt in a year. Note that this is a minimum effect and does not count additions of other ions that may be present, such as sulfate.

This salinity rise means that aquarists may have to offset that rise by removing some salt water periodically and replacing it with fresh. It may happen partly by skimming, but will also likely require some intervention. Do not rely on the above number for intervention purposes because some two parts may contain much more material (e.g., sulfate, etc.). Make the changes as you would for any other factor impacting salinity: by testing and adjusting when needed).

Further, when one lowers the salinity to offset the rise from the accumulating sodium and chloride, one is necessarily depressing every other ion in the water. For example, if you dose at the 1 dKH per day rate, do no water changes, then after a year drop the salinity by 7.5 ppt, the concentration of every ion in the water will drop by a factor of (35-7.5 ppt)/(35 ppt) to 79% of its value on the first of the year. Potassium, for example, would drop from 400 ppm to 316 pm. Even worse, magnesium is not only depressed by this factor (1300 ppm to 1027 ppm) but was also getting consumed along the way.

 

[kilnakorr]

We are talking, for example, about potassium (and every other ions except sodium or chloride).

This is the pertinent section:

Accumulating Sodium and Chloride

A very important consequence of using a two part is that sodium and chloride are added with every dose. Over time, this effect is quite significant. The actual salinity increase will vary based on exactly what other ingredients are incorporated into the two part, and in what form, but we can estimate the minimum effect one would see without water changes from just the alkalinity and calcium additions.

Assumption: add 1 dKH of alkalinity and the balanced amount of 7 ppm calcium each day. 1 dKH of alkalinity causes 0.36 meq/L of sodium to accumulate, or 8 mg/L sodium. The calcium chloride addition will add 12.4 ppm of chloride. Importantly, the Na to Cl ratio is exactly that found in NaCl, and we will come back to that later. We are thus adding 8 + 12.4 mg/l every day, or 632 mg/L in a month = 0.63 ppt each month =7.5 ppt in a year. Note that this is a minimum effect and does not count additions of other ions that may be present, such as sulfate.

This salinity rise means that aquarists may have to offset that rise by removing some salt water periodically and replacing it with fresh. It may happen partly by skimming, but will also likely require some intervention. Do not rely on the above number for intervention purposes because some two parts may contain much more material (e.g., sulfate, etc.). Make the changes as you would for any other factor impacting salinity: by testing and adjusting when needed).

Further, when one lowers the salinity to offset the rise from the accumulating sodium and chloride, one is necessarily depressing every other ion in the water. For example, if you dose at the 1 dKH per day rate, do no water changes, then after a year drop the salinity by 7.5 ppt, the concentration of every ion in the water will drop by a factor of (35-7.5 ppt)/(35 ppt) to 79% of its value on the first of the year. Potassium, for example, would drop from 400 ppm to 316 pm. Even worse, magnesium is not only depressed by this factor (1300 ppm to 1027 ppm) but was also getting consumed along the way.

I finally read it right.
I was focused on the sodium and chloride.

In short, the left over sodium and chloride from our dosing increases the salinity. Lowering the salinity, will also lower everything else in the tank, which we should be aware of.
A sodium chloride free mix, will add these lowered elements back, but obviously not increase the salinity.

 

[Randy Holmes-Farley]

I finally read it right.
I was focused on the sodium and chloride.

In short, the left over sodium and chloride from our dosing increases the salinity. Lowering the salinity, will also lower everything else in the tank, which we should be aware of.
A sodium chloride free mix, will add these lowered elements back, but obviously not increase the salinity.

Yes, except the sodium chloride free salt mix also boosts salinity, but when you correct both effects back to normal salinity, then the sodium and chloride are no longer in excess relative to things like potassium that came in wite the sodium chloride free salt mix.