Thoughts on PH and CO2

David S

Active Member
Review score
+0 /0 /-0
View Badges
Joined
Jul 23, 2016
Messages
409
Reaction score
200
Review score
+0 /0 /-0
Greetings Reefers,

So I've been down this road before; namely high PH in my reef tank.
I know many enthusiasts would love to have "high" PH in their aquaria, but believe me you do not want it to consistently go beyond 8.5 let alone rise to near 8.7, which occasionally happens in my Nano reef.
So went down to the local store to purchase some unflavored seltzer to pour into the tank, as per an article on BRS.
I had tried seltzer water in the past, but this article, you might say, triggered a "reef epiphany".
For the most part, we consider carbon dioxide the "enemy" - at least at night.
But during the day isn't it absolutely vital for driving the growth of our corals?
John (the writer of the blog) suggested that an exceedingly high PH is the result of a lack of CO2 in the tank.
When you think about it makes a bit of sense. The thing is I never really considered it.
I'm speculating that due to the large amount of LPS and SPS in my Aquarium, not to mention, the Zoa's, photosynthetic Gorgonians and Rock flower Anemones there is a high demand for CO2 resulting in a shortage, thusly causing my PH to skyrocket.
Anyway the PH was 8.48 @ about 3:10 PM when I added about a 1/2 cup of seltzer water to the tank. The PH dropped to 8.42 within 30 minutes.
It is currently back up to 8.49 (5:40 PM).
I will likely be more aggressive in adding the seltzer water, moving forward.
The other thing I should mention is the tendency for my PH to plummet at night. Usually by 0.45 - 0.50 (the last 2 weeks it's down to 0.35. I attribute that to the loss of my Flame Angel who at the time of its 9 year anniversary with me, decided to jump out of the tank!).
In any case I wonder if the huge CO2 buildup at night (Randy referred to it as "incomplete aeration") is related to the CO2 shortage during the day.
I'm wondering if the addition of the seltzer might actually moderate the PH drop at night.
For example, I have noticed that when I have added things that would depress Ph ( Rowaphos being a good exmple, as a fresh batch could drop the PH in my tank by 0.2. However, I would notice the subsequent nightly PH drop would be less pronounced.)
Anyway, I'll be looking at that.
I'm also wondering if the added CO2 will eventually cause a growth spurt in my Acros.
Time will tell.
 
Orphek OR3 reef aquarium LED lighting
OP
David S

David S

Active Member
Review score
+0 /0 /-0
View Badges
Joined
Jul 23, 2016
Messages
409
Reaction score
200
Review score
+0 /0 /-0
Interesting read. I don't have high pH, but the seltzer solution sounds very unique!
Yes.
The advantage is it only affects the PH (not alkalinity) and while Vinegar can also lower PH it can also cause a bacterial bloom.
I guess the seltzer could lower salinity, but you would need to add a lot.
 

homer1475

Figuring out the hobby one coral at a time.
Review score
+1 /0 /-0
View Badges
Joined
Apr 24, 2018
Messages
7,906
Reaction score
11,973
Review score
+1 /0 /-0
Location
Way upstate NY
Like vinegar the seltzer is only a temp solution. Once the CO2 is used up, your PH will go right back up. Similar to vinegar(although I have only heard of using vinegar to lower alk), where once the carbon is used up, the ALK goes right back up(thats why we dose vinegar as a carbon source when carbon dosing).

Not sure how one would lower PH unless you inject CO2 into the water(like a calcium reactor)?
 

Randy Holmes-Farley

Reef Chemist
Review score
+0 /0 /-0
View Badges
Joined
Sep 5, 2014
Messages
47,339
Reaction score
37,034
Review score
+0 /0 /-0
Location
Arlington, Massachusetts, United States
Interesting read. I don't have high pH, but the seltzer solution sounds very unique!

lol

Hardly. BRS is way, way late to the game.

Excessively high pH is extraordinarily rare without using very high pH additives, and can usually be solved with more aeration, but my article on high pH in 2005 clearly shows how to use CO2 as seltzer to lower pH:

High pH: Causes and Cures

Solutions to pH Problems

Some solutions to pH problems are peculiar to a specific cause, such as adding vinegar to limewater, or using less of it. Some general solutions, however, are frequently effective. My recommendations on how to deal with high pH problems are detailed below.

The most benign way to reduce high pH is to aerate the water more. Whether the aquarium looks well-aerated or not, if the pH is above 8.5 and the alkalinity is not above 4 meq/L, then the aquarium is not fully equilibrated with carbon dioxide in the air. Equilibrating carbon dioxide can be much more difficult than equilibrating oxygen. Air contains very little carbon dioxide (about 350 ppm) relative to oxygen (210,000 ppm). Consequently, a lot more air needs to be driven through the water to introduce the same amount of carbon dioxide as oxygen. Perfect aeration will solve nearly any high pH problem, and will rarely cause any problem of its own.

That said, sufficient aeration is not always easily attained, and other methods can be useful. These other methods are:

A. Direct addition of carbon dioxide. Bottled soda water (seltzer) can be used to instantly reduce aquarium pH. Be sure to select unflavored soda water, and check the ingredients to be sure it doesn't contain anything that should be avoided (phosphate, etc). Many manufacturers list water and carbon dioxide as the only ingredients.

I recommend adding 6 mL of soda water per gallon of tank water to reduce pH by about 0.3 units. Add it to a high flow area away from organisms (such as in a sump). The local pH where it first is added will be very low. Going about this procedure slowly is better than proceeding too fast. If you do not have a sump, add it especially slowly. Some soda water may have more, or less, carbon dioxide in it, and the lower the aquarium's alkalinity, the larger will be the pH drop. Also, the higher the pH, the smaller will be the pH drop, because the buffering of seawater declines steadily as the pH drops from about 9 to 7.5.


B. Direct addition of vinegar. Commercial distilled white vinegar (typically 5% acetic acid or "5% acidity") can be used to instantly reduce aquarium pH. Do not use wine vinegars as they may contain undesirable organics in addition to the acetic acid.

I recommend adding 1 mL of distilled white vinegar per gallon of tank water to initially reduce pH by about 0.3 units. Once again, add it to a high flow area away from organisms (such as in a sump). The local pH where it first is added will be very low. Going about this procedure slowly is better than proceeding too fast. If you do not have a sump, add it especially slowly. The lower the aquarium's alkalinity, the larger will be the pH drop. Also, the higher the pH, the smaller will be the pH drop, because the buffering of seawater declines steadily as the pH drops from about 9 to 7.5. Remember, there may be an additional, later drop in pH as the vinegar is metabolized to carbon dioxide.

C. Addition of vinegar via limewater. Commercial distilled white vinegar can be used to reduce tank pH by adding it to limewater that is subsequently added to the aquarium. Do not use wine vinegars as they may contain undesirable organics in addition to the acetic acid. A reasonable dose to start with is 45 ml of vinegar per gallon of limewater.
 
Fritz

Randy Holmes-Farley

Reef Chemist
Review score
+0 /0 /-0
View Badges
Joined
Sep 5, 2014
Messages
47,339
Reaction score
37,034
Review score
+0 /0 /-0
Location
Arlington, Massachusetts, United States
I'm wondering if the addition of the seltzer might actually moderate the PH drop at night.

No, it won't. At lower pH, with all other things being equal, the buffering capacity is lower, so the pH swing from consumption and addition of CO2 by photosynthesis and respiration will be larger.

I discuss pH buffering and the pH swing here:


In the case of normal seawater at pH 8.2, b = 0.19 meq/L/pH unit for the boric acid/borate system, and 0.63 meq/L/pH unit for the bicarbonate/carbonate system. These values are additive, and result in a total buffering of b = 0.82 meq/L/pH unit. Under these conditions, the boric acid/borate system provides about 23% of the total buffering, while the bicarbonate/carbonate system provides about 77%.

If the pH of normal seawater is raised to 8.5, the total buffering is b = 1.2 meq/L/pH unit, or about 40% greater than at pH 8.2 (because both systems are closer to the pKa). At this pH, the relative contribution of the two systems to the total capacity is only slightly different than at pH 8.2, with 20% from borate and 80% from carbonate.

If the pH of normal seawater is lowered to 7.8, the total buffering is b = 0.42 meq/L/pH unit, or about half that at pH 8.2 (because both systems are farther from the pKa). At this pH, the relative contribution of the two systems to the total capacity is also only slightly different than at pH 8.2, with 29% from borate and 71% from carbonate.
 

Randy Holmes-Farley

Reef Chemist
Review score
+0 /0 /-0
View Badges
Joined
Sep 5, 2014
Messages
47,339
Reaction score
37,034
Review score
+0 /0 /-0
Location
Arlington, Massachusetts, United States
We have a co2 system for our freshwater planted tank. Wonder if that would be useful to you. Runs on a timer.

Aeration is usually a much better way because it also increases O2 saturation.
 
OP
David S

David S

Active Member
Review score
+0 /0 /-0
View Badges
Joined
Jul 23, 2016
Messages
409
Reaction score
200
Review score
+0 /0 /-0
Like vinegar the seltzer is only a temp solution. Once the CO2 is used up, your PH will go right back up. Similar to vinegar(although I have only heard of using vinegar to lower alk), where once the carbon is used up, the ALK goes right back up(thats why we dose vinegar as a carbon source when carbon dosing).

Not sure how one would lower PH unless you inject CO2 into the water(like a calcium reactor)?
Yes.
I know my PH will rise. That is why I am considering adding the CO2 by use of seltzer on a regular basis
We have a co2 system for our freshwater planted tank. Wonder if that would be useful to you. Runs on a timer.
Thanks
I'm visiting my LFS later today, I'll ask them about it, as they have used CO2 for some of their planted freshwater displays.
 
OP
David S

David S

Active Member
Review score
+0 /0 /-0
View Badges
Joined
Jul 23, 2016
Messages
409
Reaction score
200
Review score
+0 /0 /-0
lol

Hardly. BRS is way, way late to the game.

Excessively high pH is extraordinarily rare without using very high pH additives, and can usually be solved with more aeration, but my article on high pH in 2005 clearly shows how to use CO2 as seltzer to lower pH:

High pH: Causes and Cures

Solutions to pH Problems

Some solutions to pH problems are peculiar to a specific cause, such as adding vinegar to limewater, or using less of it. Some general solutions, however, are frequently effective. My recommendations on how to deal with high pH problems are detailed below.

The most benign way to reduce high pH is to aerate the water more. Whether the aquarium looks well-aerated or not, if the pH is above 8.5 and the alkalinity is not above 4 meq/L, then the aquarium is not fully equilibrated with carbon dioxide in the air. Equilibrating carbon dioxide can be much more difficult than equilibrating oxygen. Air contains very little carbon dioxide (about 350 ppm) relative to oxygen (210,000 ppm). Consequently, a lot more air needs to be driven through the water to introduce the same amount of carbon dioxide as oxygen. Perfect aeration will solve nearly any high pH problem, and will rarely cause any problem of its own.

That said, sufficient aeration is not always easily attained, and other methods can be useful. These other methods are:

A. Direct addition of carbon dioxide. Bottled soda water (seltzer) can be used to instantly reduce aquarium pH. Be sure to select unflavored soda water, and check the ingredients to be sure it doesn't contain anything that should be avoided (phosphate, etc). Many manufacturers list water and carbon dioxide as the only ingredients.

I recommend adding 6 mL of soda water per gallon of tank water to reduce pH by about 0.3 units. Add it to a high flow area away from organisms (such as in a sump). The local pH where it first is added will be very low. Going about this procedure slowly is better than proceeding too fast. If you do not have a sump, add it especially slowly. Some soda water may have more, or less, carbon dioxide in it, and the lower the aquarium's alkalinity, the larger will be the pH drop. Also, the higher the pH, the smaller will be the pH drop, because the buffering of seawater declines steadily as the pH drops from about 9 to 7.5.


B. Direct addition of vinegar. Commercial distilled white vinegar (typically 5% acetic acid or "5% acidity") can be used to instantly reduce aquarium pH. Do not use wine vinegars as they may contain undesirable organics in addition to the acetic acid.

I recommend adding 1 mL of distilled white vinegar per gallon of tank water to initially reduce pH by about 0.3 units. Once again, add it to a high flow area away from organisms (such as in a sump). The local pH where it first is added will be very low. Going about this procedure slowly is better than proceeding too fast. If you do not have a sump, add it especially slowly. The lower the aquarium's alkalinity, the larger will be the pH drop. Also, the higher the pH, the smaller will be the pH drop, because the buffering of seawater declines steadily as the pH drops from about 9 to 7.5. Remember, there may be an additional, later drop in pH as the vinegar is metabolized to carbon dioxide.

C. Addition of vinegar via limewater. Commercial distilled white vinegar can be used to reduce tank pH by adding it to limewater that is subsequently added to the aquarium. Do not use wine vinegars as they may contain undesirable organics in addition to the acetic acid. A reasonable dose to start with is 45 ml of vinegar per gallon of limewater.
Thanks again Randy
Actually when I dosed yesterday, I had to increase the amount of Soda water to get a drop in PH.
Your recommendation sounds more reasonable.
 
Click to watch best scape method in 5 easy steps!
OP
David S

David S

Active Member
Review score
+0 /0 /-0
View Badges
Joined
Jul 23, 2016
Messages
409
Reaction score
200
Review score
+0 /0 /-0
No, it won't. At lower pH, with all other things being equal, the buffering capacity is lower, so the pH swing from consumption and addition of CO2 by photosynthesis and respiration will be larger.

I discuss pH buffering and the pH swing here:


In the case of normal seawater at pH 8.2, b = 0.19 meq/L/pH unit for the boric acid/borate system, and 0.63 meq/L/pH unit for the bicarbonate/carbonate system. These values are additive, and result in a total buffering of b = 0.82 meq/L/pH unit. Under these conditions, the boric acid/borate system provides about 23% of the total buffering, while the bicarbonate/carbonate system provides about 77%.

If the pH of normal seawater is raised to 8.5, the total buffering is b = 1.2 meq/L/pH unit, or about 40% greater than at pH 8.2 (because both systems are closer to the pKa). At this pH, the relative contribution of the two systems to the total capacity is only slightly different than at pH 8.2, with 20% from borate and 80% from carbonate.

If the pH of normal seawater is lowered to 7.8, the total buffering is b = 0.42 meq/L/pH unit, or about half that at pH 8.2 (because both systems are farther from the pKa). At this pH, the relative contribution of the two systems to the total capacity is also only slightly different than at pH 8.2, with 29% from borate and 71% from carbonate.
Randy,
Don't mean to contradict you, but as I suspected the PH , which peaked between 7:20 - 8 PM @ 8.55 last night (would have exceeded 8.6 if I hadn't intervened) only dropped by 0.25 from that time until 10 AM, this morning, which not too coincidentally is when my lights start coming on.
That's compared with a nightly decline of 0.35 - 0.37 since the demise of my Flame Angel.
This is consistent, IME, with what happens whenever, intentionally or accidentally, the PH is lowered during the daytime.
 

Attachments

  • Screenshot_2021-11-23-11-20-45.png
    Screenshot_2021-11-23-11-20-45.png
    203.9 KB · Views: 12
OP
David S

David S

Active Member
Review score
+0 /0 /-0
View Badges
Joined
Jul 23, 2016
Messages
409
Reaction score
200
Review score
+0 /0 /-0
So it looks like I'll be dosing soda water AKA Seltzer for the immediate future.
Not only is it an effective means for lowering my PH during the day, but it also seems to reduce the PH drop at night.
It sounds like a win/win (hope, hope).
BTW a few shots of my tank.
First, from the side:

And from the front:
 

Attachments

  • 20211123_101657.jpg
    20211123_101657.jpg
    194.7 KB · Views: 12
  • 20211123_101820.jpg
    20211123_101820.jpg
    302 KB · Views: 11

Randy Holmes-Farley

Reef Chemist
Review score
+0 /0 /-0
View Badges
Joined
Sep 5, 2014
Messages
47,339
Reaction score
37,034
Review score
+0 /0 /-0
Location
Arlington, Massachusetts, United States
Randy,
Don't mean to contradict you, but as I suspected the PH , which peaked between 7:20 - 8 PM @ 8.55 last night (would have exceeded 8.6 if I hadn't intervened) only dropped by 0.25 from that time until 10 AM, this morning, which not too coincidentally is when my lights start coming on.
That's compared with a nightly decline of 0.35 - 0.37 since the demise of my Flame Angel.
This is consistent, IME, with what happens whenever, intentionally or accidentally, the PH is lowered during the daytime.

Are you tracking and maintaining alkalinity?

Buffering and pH is highly dependent on alkalinity, and lowering the pH will lower the demand for alkalinity. Thus, if alk changes, it too will impact the daily pH swing.
 

J1a

Active Member
Review score
+0 /0 /-0
View Badges
Joined
Nov 14, 2021
Messages
184
Reaction score
335
Review score
+0 /0 /-0
Location
Singapore
Greetings Reefers,

So I've been down this road before; namely high PH in my reef tank.
I know many enthusiasts would love to have "high" PH in their aquaria, but believe me you do not want it to consistently go beyond 8.5 let alone rise to near 8.7, which occasionally happens in my Nano reef.
So went down to the local store to purchase some unflavored seltzer to pour into the tank, as per an article on BRS.
I had tried seltzer water in the past, but this article, you might say, triggered a "reef epiphany".
For the most part, we consider carbon dioxide the "enemy" - at least at night.
But during the day isn't it absolutely vital for driving the growth of our corals?
John (the writer of the blog) suggested that an exceedingly high PH is the result of a lack of CO2 in the tank.
When you think about it makes a bit of sense. The thing is I never really considered it.
I'm speculating that due to the large amount of LPS and SPS in my Aquarium, not to mention, the Zoa's, photosynthetic Gorgonians and Rock flower Anemones there is a high demand for CO2 resulting in a shortage, thusly causing my PH to skyrocket.
Anyway the PH was 8.48 @ about 3:10 PM when I added about a 1/2 cup of seltzer water to the tank. The PH dropped to 8.42 within 30 minutes.
It is currently back up to 8.49 (5:40 PM).
I will likely be more aggressive in adding the seltzer water, moving forward.
The other thing I should mention is the tendency for my PH to plummet at night. Usually by 0.45 - 0.50 (the last 2 weeks it's down to 0.35. I attribute that to the loss of my Flame Angel who at the time of its 9 year anniversary with me, decided to jump out of the tank!).
In any case I wonder if the huge CO2 buildup at night (Randy referred to it as "incomplete aeration") is related to the CO2 shortage during the day.
I'm wondering if the addition of the seltzer might actually moderate the PH drop at night.
For example, I have noticed that when I have added things that would depress Ph ( Rowaphos being a good exmple, as a fresh batch could drop the PH in my tank by 0.2. However, I would notice the subsequent nightly PH drop would be less pronounced.)
Anyway, I'll be looking at that.
I'm also wondering if the added CO2 will eventually cause a growth spurt in my Acros.
Time will tell.
Just to cover all bases, the pH probes are recently calibrated?

If I'm not mistaken, corals use bicarbonate effectively for photosynthesis. That's why I don't think they are CO2 starved. On the other hand, higher pH can increase the rate of calcification; probably leading to faster growth.
 
AquaCave Logo Banner

Randy Holmes-Farley

Reef Chemist
Review score
+0 /0 /-0
View Badges
Joined
Sep 5, 2014
Messages
47,339
Reaction score
37,034
Review score
+0 /0 /-0
Location
Arlington, Massachusetts, United States
Just to cover all bases, the pH probes are recently calibrated?

If I'm not mistaken, corals use bicarbonate effectively for photosynthesis. That's why I don't think they are CO2 starved. On the other hand, higher pH can increase the rate of calcification; probably leading to faster growth.

That is the most common cause of "high" pH:

"Make sure that there really is a pH problem. Many apparent pH problems are really measurement problems rather than real aquarium problems. This issue seems to be especially common when the aquarist is using pH test kits, rather than electronic measurement with a pH meter, but all methods can and do go wrong. Avoid turning a good situation into a bad one simply because a pH meter was not properly calibrated. Also, when not adding limewater or other high-pH additives, a pH reading above pH 8.5 is most likely an error.

Consequently, be sure to verify the pH reading before taking any but the most benign measures. Here are several articles that are worth reading on pH measurement to help ensure that the readings you are seeing are accurate:"
 
OP
David S

David S

Active Member
Review score
+0 /0 /-0
View Badges
Joined
Jul 23, 2016
Messages
409
Reaction score
200
Review score
+0 /0 /-0
So now that I have a potential solution to my high PH and assuming the cause was a lack of CO2, I wonder if the added carbon dioxide will be taken up by the corals via their Zooxantheallae.
I'm hoping that is the case. The lack of CO2 could be a reason many of my Acros have slow to no growth.
Then it could be a "be careful what you ask for" thing as my LPS grow fairly well and my Elegance and Torch are making nice so far, but that could change, particularly if each experiences a growth spurt
Are you tracking and maintaining alkalinity?

Buffering and pH is highly dependent on alkalinity, and lowering the pH will lower the demand for alkalinity. Thus, if alk changes, it too will impact the daily pH swing.
Good point.
I will monitor closely.
Currently ALK is - as per Salifert - 8.3 DKH.
This compares to 7.5 DKH reading, this past Saturday, which was performed at different time of day.
 

Randy Holmes-Farley

Reef Chemist
Review score
+0 /0 /-0
View Badges
Joined
Sep 5, 2014
Messages
47,339
Reaction score
37,034
Review score
+0 /0 /-0
Location
Arlington, Massachusetts, United States
So now that I have a potential solution to my high PH and assuming the cause was a lack of CO2, I wonder if the added carbon dioxide will be taken up by the corals via their Zooxantheallae.
I'm hoping that is the case. The lack of CO2 could be a reason many of my Acros have slow to no growth.

I don't agree. I'm not even convinced you actually have high pH nd it is not simply measurement error, but I think it is generally counterproductive to try to get increased coral growth by lowering pH.

I have never seen a study that shows better hard coral growth at lower pH, and plenty show the opposite.
 
OP
David S

David S

Active Member
Review score
+0 /0 /-0
View Badges
Joined
Jul 23, 2016
Messages
409
Reaction score
200
Review score
+0 /0 /-0
I don't agree. I'm not even convinced you actually have high pH nd it is not simply measurement error, but I think it is generally counterproductive to try to get increased coral growth by lowering pH.

I have never seen a study that shows better hard coral growth at lower pH, and plenty show the opposite.
Hmmmm....
So you think my PH monitor is inaccurate.
I will concede that I have not calibrated the probe in awhile.
I will get back to you, in a few...
 
REEFTIDE

Have you ever torn down a tank over an issue you couldn't seem to beat?

  • Yes! I have. (Tell us about what issue you faced in the thread.)

    Votes: 115 24.6%
  • No. Thankfully, I haven't.

    Votes: 244 52.1%
  • Nope, but it almost happened. (Share your experience in the thread.)

    Votes: 34 7.3%
  • Not yet, but I'm almost there. (Tell us what you're dealing with.)

    Votes: 40 8.5%
  • If you reef long enough, this will eventually happen to you.

    Votes: 30 6.4%
  • Other

    Votes: 5 1.1%
AquaCave Logo Banner
Top