Can't keep up with alkalinity consumption

[Stelioshah]

In the last few days, my alkalinity consumption has increased drastically. At the same time, my calcium does not budge, it stays within the range of 440-460ppm. I am using a saturated NaHCO3 solution to manage my alkalinity. My issue is that in the past, I would use 5mLs of this solution and the alkalinty would raise by 0.3. Now I might add 20mLs and it won't even raise by 0.15. My pH is around 8.15-8.3. The solution still is saturated since there is undissolved NaHCO3 at the bottom of the bottle. The weather is also hotter right now so the concentration of dissolved NaHCO3 should be higher. What could be causing this? I also have Ca(OH)2 at home, but I am not looking of raising Ca2+ in the water, that's why I am using the soda. There is no visible CaCO3 precipitation at the place of the dosage. What should I do?

 

[Stelioshah]

I have noticed, especially after water changing, If my alkalinity is let's say at 7.7. By adding 5-10mLs of the solution I will raise it at 8.0, but then no matter how much more I add it won't raise a bit.

 

[Lasse]

I would clean out the bottle - add some new NaHCO3 powder and new RO water and test again.

Sincerely Lasse

 

[Randy Holmes-Farley]

In the last few days, my alkalinity consumption has increased drastically. At the same time, my calcium does not budge, it stays within the range of 440-460ppm. I am using a saturated NaHCO3 solution to manage my alkalinity. My issue is that in the past, I would use 5mLs of this solution and the alkalinty would raise by 0.3. Now I might add 20mLs and it won't even raise by 0.15. My pH is around 8.15-8.3. The solution still is saturated since there is undissolved NaHCO3 at the bottom of the bottle. The weather is also hotter right now so the concentration of dissolved NaHCO3 should be higher. What could be causing this? I also have Ca(OH)2 at home, but I am not looking of raising Ca2+ in the water, that's why I am using the soda. There is no visible CaCO3 precipitation at the place of the dosage. What should I do?

What size tank are you adding this to? Without that, it is impossible to know how much you are boosting alkalinity.

It is a poor practice to use a saturated solution, IMO. You cannot know the exact potency as it will change with temperature, and you cannot even be sure it is still saturated and the solids are not something else.

I recommend making a more standard solution, such as one of my DIY two part recipes:

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

 

[Stelioshah]

I would clean out the bottle - add some new NaHCO3 powder and new RO water and test again.

Sincerely Lasse

Unfortunately I already tried a new solution and I had the same results..

 

[Stelioshah]

What size tank are you adding this to? Without that, it is impossible to know how much you are boosting alkalinity.

It is a poor practice to use a saturated solution, IMO. You cannot know the exact potency as it will change with temperature, and you cannot even be sure it is still saturated and the solids are not something else.

I recommend making a more standard solution, such as one of my DIY two part recipes:

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

It is 42gallons, what I do not understand is why the alkalinity raise is not linear. A small volume will raise it at first but then it won't raise more. Would calcium raise quickly if I used a supplement with calcium? I have not tried it yet.

 

[Randy Holmes-Farley]

It is 42gallons, what I do not understand is why the alkalinity raise is not linear. A small volume will raise it at first but then it won't raise more. Would calcium raise quickly if I used a supplement with calcium? I have not tried it yet.

It's very hard to judge how much alk you are actually adding with a "saturated" solution, but my expectation is that you are not adding more than twice the amount as if you made by DIY using unbaked sodium bicarbonate.

Using my DIY using unbaked bicarbonate to add 5 mL to 42 gallons boosts alk by a tad less than 0.1 dKH. Adding 20 mL boosts alk by 0.34 dKH.

What material exactly are you using to make this dosing solution?

How are you measuring alkalinity?

I strongly suggest switching to a nonsaturated solution so you can know exactly what you are dosing.

Recipe #2, Part 2: The Alkalinity Part

Dissolve 297 grams of baking soda (about 1 1/8 cups) in enough water to make 1 gallon total. This dissolution may require a fair amount of mixing. Warming it speeds dissolution. This solution will contain about 950 meq/L of alkalinity (2660 dKH). As mentioned earlier, Arm & Hammer is a fine brand of baking soda to use in these recipes. Be sure to NOT use baking powder. Baking powder is a different material that often has phosphate as a main ingredient.

 

[Stelioshah]

It's very hard to judge how much alk you are actually adding with a "saturated" solution, but my expectation is that you are not adding more than twice the amount as if you made by DIY using unbaked sodium bicarbonate.

Using my DIY using unbaked bicarbonate to add 5 mL to 42 gallons boosts alk by a tad less than 0.1 dKH. Adding 20 mL boosts alk by 0.34 dKH.

What material exactly are you using to make this dosing solution?

How are you measuring alkalinity?

I strongly suggest switching to a nonsaturated solution so you can know exactly what you are dosing.

Recipe #2, Part 2: The Alkalinity Part

Dissolve 297 grams of baking soda (about 1 1/8 cups) in enough water to make 1 gallon total. This dissolution may require a fair amount of mixing. Warming it speeds dissolution. This solution will contain about 950 meq/L of alkalinity (2660 dKH). As mentioned earlier, Arm & Hammer is a fine brand of baking soda to use in these recipes. Be sure to NOT use baking powder. Baking powder is a different material that often has phosphate as a main ingredient.

I saw your recipe 2. I will need to buy CaCl2 to make the solution..

To make the solution I use in my dosing pump, I used NaHCO3 ash in a bottle of ro water, I bought this product from a reef shop, I believe that it actually is NaHCO3 based on some pH measurements that I did (and not something else such us Na2CO3).

I let the undissolved ash sit and then mixed the solution. I repeated this 3-4 times. I know that the solid that does not dissolve is the ash and not some other impurity, because after adding some more ash into the bottle it always stayed undissolved.

I then took the solution and passed it through a filter, that's the solution I used into my doser.

When manually adding, I use the remaining liquid from the original mixing container, which still has a solid layer at the bottom of it. That's what I am reffering to here.

I will try your recipe and see how much it affects my calcium.

 

[Stelioshah]

Oh I just realized that I could just use the bicarbonate part of your recipe 2 solution.. So I am not going to have an issue.

Do you know of any semi-accurate ways to see if I am actually using Na2CO3 or NaHCO3?

 

[Randy Holmes-Farley]

I saw your recipe 2. I will need to buy CaCl2 to make the solution..

Just make the alk part and try using that.

This calculator shows the boost it will give:

http://reef.diesyst.com/chemcalc/chem_calc3.html

To make the solution I use in my dosing pump, I used NaHCO3 ash in a bottle of ro water, I bought this product from a reef shop, I believe that it actually is NaHCO3 based on some pH measurements that I did (and not something else such us Na2CO3).

It now sounds like you are using sodium carbonate, not sodium bicarbonate. Soda ash is sodium carbonate, Baking soda is sodium bicarbonate. Is it repackaged by a reef shop, or doe it have a brand name?

I would stop using it and use a known chemical.

 

[Randy Holmes-Farley]

Oh I just realized that I could just use the bicarbonate part of your recipe 2 solution.. So I am not going to have an issue.

Do you know of any semi-accurate ways to see if I am actually using Na2CO3 or NaHCO3?

NaHCO3 when added to seawater initially causes a small pH drop (~0.06 pH unit drop per 1.4 dKH added) while sodium carbonate causes a substantial pH rise (~0.35 pH unit rise per 1.4 dKH added).

 

[Stelioshah]

Just make the alk part and try using that.

This calculator shows the boost it will give:

http://reef.diesyst.com/chemcalc/chem_calc3.html


It now sounds like you are using sodium carbonate, not sodium bicarbonate. Soda ash is sodium carbonate, Baking soda is sodium bicarbonate. Is it repackaged by a reef shop, or doe it have a brand name?

I would stop using it and use a known chemical.

It unfortunately is not branded and does not have a name, I bought it years ago. I tried checking if the pH of a solution of the substance, matched the pH I would expect of a NaHCO3 or Na2CO3. It seemed to match NaHCO3 but my method definitely was inaccurate.

I will be changing water today, I will test for the pH change when using the solution and act accordingly. Thanks for the replies.