Alkalinity Dosing with ATO

Reef Alchemy

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Hello All,

I've been dosing Red Sea dry Sodium Bicarbonate mixed in with my RO/DI auto topoff water in the typical float valve configuration. The alkalinity has been maintained consistently this way. However, I have low pH (7.6 morning to 7.8 evening) and I want to increase it with Sodium Hydroxide (target range of 8.0-8.1morning and 8.2-8.3 in the evening). Can Sodium Hydroxide be mixed with Sodium Bicarbonate in the ATO?... or will it just precipitate Sodium Carbonate? Or would it be better to use Sodium carbonate in conjunction with Sodium Hydroxide? Or will I have to drip the Sodium Hydroxide separately? Dripping Sodium Hydroxide with a secondary container creates its' own complications. I currently don't have an array of peristaltic pumps (which I want to eventually get) to dose with.

I have never dosed Sodium Carbonate instead of Sodium Bicarbonate. Is Sodium Carbonate by itself enough to increase the pH instead of using Sodium Hydroxide?

Thank You for your responses.

Red Sea 425 XL 88-gallon display.

Edit: I tried Kalkwasser. Dosing until the alkalinity reached 9.5. The pH was still 7.8. I checked the Calcium and it was 800ppm!!! So Kalkwasser is a no go.

Also, I was dosing Brightwell pH Boost, but the product is pretty weak (pH 10.8). I was dosing 150ml a day and I didn't even get the pH into the 8.0's. It would be a logistic nightmare and too expensive to use that product.

Oh, I don't use a calcium reactor... I dose Calcium Chloride manually as needed.
 
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World Wide Corals

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The standard way to dose sodium hydroxide is by using a 2 part system. 500g of calcium chloride from BRS and 283g of food-grade sodium hydroxide in separate 1-gallon containers. Dose equal amounts of each solution.


The easiest way is to use kalkwasser to maintain alkalinity and calcium in their acceptable ranges. The pH boost will be the same via kalkwasser vs. sodium hydroxide if you retain the same alkalinity.


Recalibrate your pH probe; if it’s still too low and you are positive your alkalinity is within 7-11dKH: address the high CO2 in your home.


Never dose a pH-boosting additive to elevate the pH; alkalinity will always rise with such solutions. Instead, use the liquid to maintain alkalinity.
 

Randy Holmes-Farley

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You can combine sodium bicarbonate/carbonate/hydroxide solutions in any ratio you want. A 1:1 molar combination of sodium bicarbonate and sodium hydroxide is identical to a sodium carbonate solution.

Just make sure your ATO system can handle high pH without issue.
 
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Edit: I tried Kalkwasser. Dosing until the alkalinity reached 9.5. The pH was still 7.8. I checked the Calcium and it was 800ppm!!! So Kalkwasser is a no go.
I'm going to say the 800ppm was a testing error. Kalkwasser doses alkalinity and calcium in equal parts, so if calcium really was 800ppm then alkalinity would have been way higher
 

Randy Holmes-Farley

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I'm going to say the 800ppm was a testing error. Kalkwasser doses alkalinity and calcium in equal parts, so if calcium really was 800ppm then alkalinity would have been way higher

Agreed. If alk boosts 2.8 dKH, calcium will only rise 20 ppm.
 
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The standard way to dose sodium hydroxide is by using a 2 part system. 500g of calcium chloride from BRS and 283g of food-grade sodium hydroxide in separate 1-gallon containers. Dose equal amounts of each solution.


The easiest way is to use kalkwasser to maintain alkalinity and calcium in their acceptable ranges. The pH boost will be the same via kalkwasser vs. sodium hydroxide if you retain the same alkalinity.


Recalibrate your pH probe; if it’s still too low and you are positive your alkalinity is within 7-11dKH: address the high CO2 in your home.


Never dose a pH-boosting additive to elevate the pH; alkalinity will always rise with such solutions. Instead, use the liquid to maintain alkalinity.
Thank you.
 
RAP Orlando
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Reef Alchemy

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I'm going to say the 800ppm was a testing error. Kalkwasser doses alkalinity and calcium in equal parts, so if calcium really was 800ppm then alkalinity would have been way higher
I may revisit Kalkwasser again then. I was using Red Sea Pro Calcium titration test, which has always appeared consistent and accurate in the past. I already have the drip-container which I was considering switching to Sodium Hydroxide.

Thanks for the response.
 
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Agreed. If alk boosts 2.8 dKH, calcium will only rise 20 ppm.
Thanks Randy. I may revisit Kalkwasser again. It may have been a Calcium testing error. I use the Red Sea Pro calcium titration test to test for Calcium and its' pretty simple to use, not sure how I could have messed it up. I should have rechecked twice just as a precaution. I was surprised at the 800 ppm Calcium result and immediately stopped dosing the Kalk. I will have to experiment and see which component works better, kalk or Soda Ash. Kalk cannot be used with my ATO, too much slurry. Soda may behave just like Kalk, producing a slurry in which only the supernatant can be dosed. I will let you know what happens.
 
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Agreed. If alk boosts 2.8 dKH, calcium will only rise 20 ppm.
Update: I believe the original Calcium test was an error as you suspected. I run daily Alkalinity tests which use 10ml of tank water and I think I performed the Calcium test with 10ml instead of the required 5ml for Calcium out of habit.

Calcium = 400 ppm.

I posed the original thread question based on Brightwells pH+ booster which is a mixture of potassium and sodium chlorides which states that the product would not raise alkalinity. I assumed Sodium Hydroxide would not increase alkalinity so that I would have to dose a buffer in conjunction with the Sodium Hydroxide. The Sodium Hydroxide I dosed increased the alkalinity significantly. Now, Sodium Hydroxide is all I am currently dosing for alkalinity/pH.
The pH boosting product is very misleading. It destroys my confidence in that company.

I also decided not to dose Sodium Hydroxide with the ATO due to the risk of catastrophic failure, which would probably ultimately happen with the sumps float valve and opted to dose with a drip-container.

For my 100-gallon system, I started dosing Sodium Hydroxide. I was able to raise the pH and keep it in the 8.2 to 8.3 range (no more that 0.2 pH increase per day, from 7.6 to 8.2), but the dkh alkalinity was increasing 0.5 dkh per day; from 9.5 to 11.8 over the period of about 4 days, so I had to back off on the Sodium Hydroxide. I did not want to go over 12 dkh. I have lowered the Sodium Hydroxide concentration I am dosing, so that the alkalinity does not exceed 11dkh, which currently means a daily pH range of 8.0 to 8.1 for the tank. I can't really keep the pH any higher without problematic levels of alkalinity.

I prefer the Sodium Carbonate method to Kalkwasser because it is easier. There is no precipitation in the drip- container and there is no noticeable reaction to atmospheric CO2 like you supposedly have to avoid with Kalkwasser. There is no need for a kalk stirrer etc.

One interesting phenomenon with my drip-container that others may want to duplicate/experiment with. I have about a 2-gallon container that I dose with. The container is sort of narrow and tall. What I do is: at night about 10:00pm, when the pH in the tank starts to normally drop, I fill the container up for the day. Since the container is more full at this time, the drip rate is higher due to the head pressure. As the night progresses and the container is more empty, the drip rate is much less when the lights come on and less is needed throughout the day. I was able to maintain a day/night swing cycle pH difference of 0.05 (say 8.2-8.25), which before I started dosing was a daily swing of 0.2 pH. I dose a half teaspoon of Sodium Hydroxide in a half gallon of RODI water per day (I was dosing 1.5 teaspoons of Sodium Hydroxide per day, to keep the pH at 8.25, but I had to back off due to the steady rise in alkalinity).

If you don't mind me asking, which brand of salt mix do you use? Red Sea Coral Pro Salt (black bucket) has a dkh of 11.5 which is closer to what my system is now.

When my system had a daily pH range of 7.6 to 7.8 (which I didn't realize until I started using the Hanna pH probe, model HI98108), I would do a water change with Red Sea Coral Pro blue bucket and my corals would stress. The Red Sea Salt has a pH of 8.3 (which is fine) and my tank was getting pH stress during water changes.
 
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I posed the original thread question based on Brightwells pH+ booster which is a mixture of potassium and sodium chlorides which states that the product would not raise alkalinity. I assumed Sodium Hydroxide would not increase alkalinity so that I would have to dose a buffer in conjunction with the Sodium Hydroxide. The Sodium Hydroxide I dosed increased the alkalinity significantly. Now, Sodium Hydroxide is all I am currently dosing for alkalinity/pH.
The pH boosting product is very misleading. It destroys my confidence in that company.

That is not quite correct. The Brightwell product is a mixture of sodium and potassium HYDROXIDES, which do boost alkalinity. Chlorides have no effect at all on pH or alkalinity.

Yes, I have no confidence in Brightwell understanding anything chemically related, including their own products. That's the most positive spin one can put on such obviously false claims. There are also much darker possible reasons.
 

Randy Holmes-Farley

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If you don't mind me asking, which brand of salt mix do you use? Red Sea Coral Pro Salt (black bucket) has a dkh of 11.5 which is closer to what my system is now.

I don't currently have a reef tank, but for 20 years I used normal IO and think it is a fine mix.
 
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Reef Alchemy

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I posed the original thread question based on Brightwells pH+ booster which is a mixture of potassium and sodium chlorides which states that the product would not raise alkalinity. I assumed Sodium Hydroxide would not increase alkalinity so that I would have to dose a buffer in conjunction with the Sodium Hydroxide. The Sodium Hydroxide I dosed increased the alkalinity significantly. Now, Sodium Hydroxide is all I am currently dosing for alkalinity/pH.
The pH boosting product is very misleading. It destroys my confidence in that company.
Sorry, I meant to originally type Potassium and Sodium Hydroxides in the above paragraph. Thank you for pointing that out.
 

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