If its not CO2, then why low pH

[RobB'z Reef]

I am planning on an external recirculating skimmer myself for a larger build. I know I suggested this in the thread, but it would be great if there was a way to make a standard prediction for recommending air draw vs volume = effect on pH.

If I would use this estimate 400 liter per hour air / 28 gallons = 14.3 liters per gallon rating in my set up in my environment

So if I wanted a 175 gallon tank, I need an air draw of around 2,500 liters per hour to get similar performance in pH. Though i do understand there’s many other variables in play, like life stock differences and equipment variables.
That’s a very large skimmer, but I’m crazy enough to do it. I can always throttle back the skimmer flow rate, and air draw.

I like what you're driving at. You'd have to base it on a set ambient CO2 level in the room as a baseline or something. Be cool to plot known CO2 levels with known air volume. Probably tank surface area etc. My guess is there are more than a few impactful variables here. Not sure they could ever nail that down. However measuring some of this could help in giving directions to predicable outcomes for other Reefers. I have a 180 gal. Tank with a 60" x 18" sump with decent flow through it. Good stuff!

 

[Ashibashi]

Hey. Im a newbie to the reef hobby, but I do biochemistry for a living and this is my favorite kind of problem.

How quickly does the pH fall back to its stable low range after you correct it up?

How often do you clean your sand? How old is this system?

Could you please check your ammonia levels and the stable baseline pH, correct the pH up to 8.1, and then check the ammonia levels again?

It could be possible that there is a buildup of anaerobic bacteria in your substrate producing acids and buffering species with dissociation constants closer to the stable pH range you're stuck at. If there was an ammonia spike at any point in the past, that could have dropped your pH and shifted the equilibrium of ammonia:ammonium toward ammonium. Bacteria can't consume ammonium so that would have reduced the populations of aerobic species on rock surfaces and in the water column. Now you're stuck with a population better suited to those conditions and sticking your pH where you dont want it.

If this is happening you will detect a sudden increase in ammonia when you force up the pH toward 8.1 or so. Maybe a deep clean is in order.

 

[GoVols]

VEE GEE Salinity Refractometer

https://www.grainger.com/product/8C...7eeb4414ea4e13c5cbaa24b95fb48ad9&gclsrc=3p.ds

I highly recommend this refractometer. Its very weighty and heavy in your hand. The scale is really easy to read.

Apex Salinity Probe (Recently Cleaned and Recalibrated (manual mode with TC 2.3%) very readings stable and repeatable.

+1 on the Vee Gee STX-3

​

​

Caught it on sale for about $80.00 in 2018

 

[Randy Holmes-Farley]

Hey. Im a newbie to the reef hobby, but I do biochemistry for a living and this is my favorite kind of problem.

How quickly does the pH fall back to its stable low range after you correct it up?

How often do you clean your sand? How old is this system?

Could you please check your ammonia levels and the stable baseline pH, correct the pH up to 8.1, and then check the ammonia levels again?

It could be possible that there is a buildup of anaerobic bacteria in your substrate producing acids and buffering species with dissociation constants closer to the stable pH range you're stuck at. If there was an ammonia spike at any point in the past, that could have dropped your pH and shifted the equilibrium of ammonia:ammonium toward ammonium. Bacteria can't consume ammonium so that would have reduced the populations of aerobic species on rock surfaces and in the water column. Now you're stuck with a population better suited to those conditions and sticking your pH where you dont want it.

If this is happening you will detect a sudden increase in ammonia when you force up the pH toward 8.1 or so. Maybe a deep clean is in order.

I do not believe there are much in the way of natural organics that buffer seawater in the range of pH that we are at (say, 7.5 to 8.5).

Most natural buffering is by carboxylic acids at much lower pH (say, 4-6) and amines at much higher pH (say, 9-11).

 

[Ashibashi]

I do not believe there are much in the way of natural organics that buffer seawater in the range of pH that we are at (say, 7.5 to 8.5).

Most natural buffering is by carboxylic acids at much lower pH (say, 4-6) and amines at much higher pH (say, 9-11).

Is there a book or source you recommend for reef chemistry?

 

[Randy Holmes-Farley]

Is there a book or source you recommend for reef chemistry?

I'd start here:

Randy's Reef Chemistry Articles

While there are many good articles out there on reef chemistry topics, here's a list of my articles. Some of them need updating, and we'll be posting revisions at R2R, but there are not many things which I think are incorrect. Handy Calculators (I don't claim to have written these, but they...

www.reef2reef.com

 

[Ashibashi]

I'd start here:

Randy's Reef Chemistry Articles

While there are many good articles out there on reef chemistry topics, here's a list of my articles. Some of them need updating, and we'll be posting revisions at R2R, but there are not many things which I think are incorrect. Handy Calculators (I don't claim to have written these, but they...

www.reef2reef.com

This is just the thing I've been looking for. Super interesting stuff. Thanks!

I'm really surprised to find out that the concentration of CO2 indoors could be so different from outdoors that it impacts the pH of water to such an extent. The last I heard about this topic was an article debunking the idea that houseplants were capable of shifting the CO2 or oxygen concentration of an indoor environment appreciably. The main points they made were that CO2 makes up an extremely small fraction of the air in the first place, and that houses aren't airtight. It boiled down to stating that in order to make any appreciable difference you'd need to basically fully occupy the floorspace with plants.

Given the difference in pH shift in water aerated inside vs outside, do you think houseplants actually might help some? Do you think CO2 exchange at the surface is the main way that acid is getting into the system? I'm confused that putting the skimmer source line outside didn't make a difference. Surely that's a much larger surface interaction over time than the tank surface is. And why is low pH not a more ubiquitous problem in household tanks?

anyway. I ramble. Big surprising mystery. Very intrigued. Gonna spend the next few days devouring the articles linked. Cheers!

 

[Biologic]

+1 on the Vee Gee STX-3

​

​

Caught it on sale for about $80.00 in 2018

Worth every penny. Big scale. Sharp optics. Not temperamental.

The thing is, most people wouldn't dare spend that much due to most refractometers being priced substantially lower. Inaccurate salinity is probably a much bigger undiagnosed problem in this hobby than most people be willing to bet on. I had three refractometers give me wildly different results even when calibrated.

This is just the thing I've been looking for. Super interesting stuff. Thanks!

I'm really surprised to find out that the concentration of CO2 indoors could be so different from outdoors that it impacts the pH of water to such an extent. The last I heard about this topic was an article debunking the idea that houseplants were capable of shifting the CO2 or oxygen concentration of an indoor environment appreciably. The main points they made were that CO2 makes up an extremely small fraction of the air in the first place, and that houses aren't airtight. It boiled down to stating that in order to make any appreciable difference you'd need to basically fully occupy the floorspace with plants.

Given the difference in pH shift in water aerated inside vs outside, do you think houseplants actually might help some? Do you think CO2 exchange at the surface is the main way that acid is getting into the system? I'm confused that putting the skimmer source line outside didn't make a difference. Surely that's a much larger surface interaction over time than the tank surface is. And why is low pH not a more ubiquitous problem in household tanks?

anyway. I ramble. Big surprising mystery. Very intrigued. Gonna spend the next few days devouring the articles linked. Cheers!

Low pH is ubiquitous in this hobby. You'll find that people are obsessing over pH now-a-days, because stable alkalinity has been for the most part been solved with the help of this forum, proper equipment/ products available, and Randy's articles. So we need something else to obsess over. Stable (or even low variability) pH is just that next beast to conquer and I think the last frontier for the basic major inorganic chemistry we have to tackle.

People say don't worry about it, but it's something that can be solved or lessen in its impact. There's no reason to just accept it if you can do a few simple things like running an airline outside. Every bit can help.

Hey. Im a newbie to the reef hobby, but I do biochemistry for a living and this is my favorite kind of problem.

How quickly does the pH fall back to its stable low range after you correct it up?

How often do you clean your sand? How old is this system?

Could you please check your ammonia levels and the stable baseline pH, correct the pH up to 8.1, and then check the ammonia levels again?

It could be possible that there is a buildup of anaerobic bacteria in your substrate producing acids and buffering species with dissociation constants closer to the stable pH range you're stuck at. If there was an ammonia spike at any point in the past, that could have dropped your pH and shifted the equilibrium of ammonia:ammonium toward ammonium. Bacteria can't consume ammonium so that would have reduced the populations of aerobic species on rock surfaces and in the water column. Now you're stuck with a population better suited to those conditions and sticking your pH where you dont want it.

If this is happening you will detect a sudden increase in ammonia when you force up the pH toward 8.1 or so. Maybe a deep clean is in order.

As for cleaning sand, I do not, because its just another cofounding variable to address. Sand is something I am thinking about eliminating totally to see if it's a contributing part of the problem. I do not want to disturb the micro-biome. I do have a very shallow >1 inch sanded.

The pH never stays stuck, but what does happen is the diurnal shift down, which is when the algae in the tank no-longer is performing photosynethic respiration. Light on - pH shoots up. CO2 is consumed.

I do like your thoughts on this.. That's going to be more difficult to monitor, but now that we have automatic testing systems, it's possible. Probes, would be extremely costly.

I would like Randy to expand on his reasoning for my understanding, which I think I understand what he's saying there. If anything, the buffer from amines would help this situation? CO2 is the main enemy because its the chief by-product of most of everything in the tank. Right?

​

Do you think CO2 exchange at the surface is the main way that acid is getting into the system?

I know it seems hard to accept at first, but once I performed the aeration test OUTSIDE, which is driving off the excess CO2 that's in solution of the tank water, the pH goes up. Its thought (more or less a fact at this point) that CO2 concentrations are higher inside, than they are outside. Taking the same test, but doing it INSIDE, pushes the pH down.

It's a simple test that I did as a teenage in chemistry class with a pH indicator in a cup of water, blowing into the water with a straw, the pH indicator turns GREEN when the solution's pH is around 6.0. CO2 decreases the pH of the water going into solution. We all breath it out -- CO2, and its in our homes, and sucked into our aquariums with our skimmer.

josephxsxn - https://www.reef2reef.com/threads/co2sys-marine-tank-table-for-ph-dkh-co2.786401/​

Look at this signature with this table. It's a predictive value of Alkalinity CO2 concentration and pH.




So my theory is using OUTSIDE air in a skimmer, can make an impact -- ONLY IF the volume of air being drawn in, can overcome the tank gas exchange of the surface of the water, and the concentration of CO2 that's in that indoor environment. So in my example, I am using a skimmer that's rated (which ratings can be ambiguous or arbitrary) 5x times the rated size for my tank to receive only as of right now, 0.1 average daily influence in my pH.

This is also a reason why CO2 Scrubbers may not work for some people due to the amount of air-draw volume being too little for their environment and size of the tank. An undersized skimmer may not have the power to run it properly.

 

[blasterman]

I feel you with the small tank. I am trying not to let size limit what I can do on this small tank, as I want to get back into a larger tank one day. So this is proof of concept that has to be scaled.

I am hesitant to try NaOH because of potential of alkalinity contribution (swings) + throwing salinity off. Likewise, CaOH throwing off Calcium.

Is the consumption from your corals, greater than what's being contributed from the NaOH? Are there any alkalinity swings at night as a result of dosing at night? Care to share how you are doing this?

You lost me at "throwing salinity off".

If you already dont have significant alk consumption there's no sense increasing pH or worrying about.

 

[Biologic]

You lost me at "throwing salinity off".

If you already dont have significant alk consumption there's no sense increasing pH or worrying about.

Significant is relative. What is significant? What would it be with a proper natural sea water pH? If I can make safe simple steps to manage my pH without kalkwasser, why wouldn't I try? 7.83 average low to the new low of 7.96 just by a bigger skimmer and outside air.

Throwing salinity off with dosing kalkwasser to control pH. I am not sure how much it would take to "control" my tank without throwing off salinity, and dumping kalkwasser in.

Now that I've bumped up my low pH from the night time by putting on a bigger skimmer, it should be easier to manage with kalkwasser.

 

[PeterZammetti]

So chasing the dragon here -- can't get above 8.01 units

>Surface Agitation --- NO EFFECT
>Opening windows --- NO EFFECT
>Running an oversized recirculating CO2 scrubber --- NO EFFECT
>Running line outside of the house, with recirculating skimmer --- NO EFFECT
>Keeping alkalinity rock steady --- NO EFFECT
>Combining everything above --- NO EFFECT
>Reading Randy's Article --- NO EFFECT

>Kalkwasser drip --- obvious positive effect but difficult in an 28 gallon all-in-one

What I haven't tried --

>Using soda ash for alkalinity -- I use ALL4Reef Calcium Formate at a rate of 15.5 mL per day.
>refugium, difficult to add on an AIO.

POSSIBLE Contributing Factors ?? --

>Two small damsels, one small clown, one small pseudochromis, 10 snails, mostly SPS
>Calcium Formate? Maybe? That's the other thing I can think of at this point
>Decay of bacterial population contributing to depressed pH

Concerns --

Since I stopped using kalkwasser a month ago as my primary method of calcium and alkalinity supplement due to safety concerns and limited ability to control the dose, my pH has been in the pits. 7.65 at night. Yes I've calibrated my probes, and checked them against some standard solutions. I am at a lost.

My sps have definitely stopped growing since I switched from kalkwasser. My alkalinity consumption has slowed down.

I just recently had the first issue I have ever had with PH in the last 28 years.
Like a madman I tried everything under the sun to try and raise and keep it up.
Now, the funny thing was when I found out what the issue was I felt so dumb because it was the only thing I overlooked.
Because I was doing a YouTube Blog to teach how to do a full reef successfully for under1k, I overlooked that my lighting was ok for a reef but not high end for what my future corals would be. The minute I threw the AI Hydra on the PH went up to 8.4 and 8.2 at night immediately, so even if your lights are high end, their age can effect this as well. LED says 8-10 years but truthfully they are in the 3-4 year range before they need replaced.

 

[Ashibashi]

Worth every penny. Big scale. Sharp optics. Not temperamental.

The thing is, most people wouldn't dare spend that much due to most refractometers being priced substantially lower. Inaccurate salinity is probably a much bigger undiagnosed problem in this hobby than most people be willing to bet on. I had three refractometers give me wildly different results even when calibrated.



Low pH is ubiquitous in this hobby. You'll find that people are obsessing over pH now-a-days, because stable alkalinity has been for the most part been solved with the help of this forum, proper equipment/ products available, and Randy's articles. So we need something else to obsess over. Stable (or even low variability) pH is just that next beast to conquer and I think the last frontier for the basic major inorganic chemistry we have to tackle.

People say don't worry about it, but it's something that can be solved or lessen in its impact. There's no reason to just accept it if you can do a few simple things like running an airline outside. Every bit can help.




As for cleaning sand, I do not, because its just another cofounding variable to address. Sand is something I am thinking about eliminating totally to see if it's a contributing part of the problem. I do not want to disturb the micro-biome. I do have a very shallow >1 inch sanded.

The pH never stays stuck, but what does happen is the diurnal shift down, which is when the algae in the tank no-longer is performing photosynethic respiration. Light on - pH shoots up. CO2 is consumed.

I do like your thoughts on this.. That's going to be more difficult to monitor, but now that we have automatic testing systems, it's possible. Probes, would be extremely costly.

I would like Randy to expand on his reasoning for my understanding, which I think I understand what he's saying there. If anything, the buffer from amines would help this situation? CO2 is the main enemy because its the chief by-product of most of everything in the tank. Right?

​

I know it seems hard to accept at first, but once I performed the aeration test OUTSIDE, which is driving off the excess CO2 that's in solution of the tank water, the pH goes up. Its thought (more or less a fact at this point) that CO2 concentrations are higher inside, than they are outside. Taking the same test, but doing it INSIDE, pushes the pH down.

It's a simple test that I did as a teenage in chemistry class with a pH indicator in a cup of water, blowing into the water with a straw, the pH indicator turns GREEN when the solution's pH is around 6.0. CO2 decreases the pH of the water going into solution. We all breath it out -- CO2, and its in our homes, and sucked into our aquariums with our skimmer.

josephxsxn - https://www.reef2reef.com/threads/co2sys-marine-tank-table-for-ph-dkh-co2.786401/​

Look at this signature with this table. It's a predictive value of Alkalinity CO2 concentration and pH.




So my theory is using OUTSIDE air in a skimmer, can make an impact -- ONLY IF the volume of air being drawn in, can overcome the tank gas exchange of the surface of the water, and the concentration of CO2 that's in that indoor environment. So in my example, I am using a skimmer that's rated (which ratings can be ambiguous or arbitrary) 5x times the rated size for my tank to receive only as of right now, 0.1 average daily influence in my pH.

This is also a reason why CO2 Scrubbers may not work for some people due to the amount of air-draw volume being too little for their environment and size of the tank. An undersized skimmer may not have the power to run it properly.

I bet I'm underestimating the amount of air to water contact a skimmer contributes because I've never used one before. Also after having a bit of a think I realize - doesn't most of the water that interacts with skimmer air just end up in the nastiness cup?

Another thought im curious about - is OP's tank in their bedroom? If the pH drops substantially at night, I would think a human breathing in a closed room would be a bigger contribution to the balance than corals respiring the opposite direction during the day. In terms of units of carbon per hour, I'd be extremely surprised if a tank of corals outpaced even a small adult human. Supposing this is an effect that gets worse over time as CO2 builds up day after day, could higher pH slowly be achieved over time by keeping the windows open at night?

 

[Ashibashi]

I just recently had the first issue I have ever had with PH in the last 28 years.
Like a madman I tried everything under the sun to try and raise and keep it up.
Now, the funny thing was when I found out what the issue was I felt so dumb because it was the only thing I overlooked.
Because I was doing a YouTube Blog to teach how to do a full reef successfully for under1k, I overlooked that my lighting was ok for a reef but not high end for what my future corals would be. The minute I threw the AI Hydra on the PH went up to 8.4 and 8.2 at night immediately, so even if your lights are high end, their age can effect this as well. LED says 8-10 years but truthfully they are in the 3-4 year range before they need replaced.

This is an awesome observation. Were you using an electronic pH meter? Wondering if electrical interference could have been the issue.

 

[PeterZammetti]

This is an awesome observation. Were you using an electronic pH meter? Wondering if electrical interference could have been the issue.

Oh, no it was the actual intensity. When the high end higher intensity lights hit the water, it changed the gas exchange amazingly in 12 hours. I was getting 7.8night and maybe 8.0day then it became 8.2/8.4 in less than a day. Now keep in mind I was monitoring for 3 months, everyday so I know factually it was just the lights being too low. I never would have caught this but because I was using the bare minimum for the project it was a finnex marine 24/7 reef light.

 

[Randy Holmes-Farley]

I'm really surprised to find out that the concentration of CO2 indoors could be so different from outdoors that it impacts the pH of water to such an extent. The last I heard about this topic was an article debunking the idea that houseplants were capable of shifting the CO2 or oxygen concentration of an indoor environment appreciably. The main points they made were that CO2 makes up an extremely small fraction of the air in the first place, and that houses aren't airtight. It boiled down to stating that in order to make any appreciable difference you'd need to basically fully occupy the floorspace with plants.

That is true. I explain that every time it comes up.

Plants just cannot take up nearly as much CO2 as you exhale in a day, unless it is a greenhouse sort of environment. The nonmeaurement way is to just recognize that the plants need to add about as much dry mass per day by photosynthesis as you eat in dry mass (and exhale as CO2) to offset the CO2 rise.

 

[Randy Holmes-Farley]

Throwing salinity off with dosing kalkwasser to control pH. I am not sure how much it would take to "control" my tank without throwing off salinity, and dumping kalkwasser in.

Kalkwasser has no significant impact on salinity.

 

[Randy Holmes-Farley]

I would like Randy to expand on his reasoning for my understanding, which I think I understand what he's saying there. If anything, the buffer from amines would help this situation? CO2 is the main enemy because its the chief by-product of most of everything in the tank. Right?

​

I don't think that natural organic buffers are contributing detectable to reef tank pH stability. The water is already heavily buffered by bicarbonate/carbonate and borate/boric acid.

I discuss pH buffering of seawater here:

Chemistry And The Aquarium: Boron In A Reef Tank

This article also discusses the sources and sinks for boron in reef tanks, and shows that while typical tanks may be slightly depleted in boron with respect to natural levels, most are not so significantly depleted that any correction is required. Nevertheless, how to test for and supplement...

reefs.com

 

[Overbrook]

OUTSIDE air in a skimmer, can make an impact -- ONLY IF the volume of air being drawn in, can overcome the tank gas exchange of the surface of the water, and the concentration of CO2 that's in that indoor environment.

Thanks for starting, and keeping going, a great thread. I agree with that statement above.

A question, that I can't seem to find the answer to: Did you ever increase the diameter of your outside air feeding line? It was raised that maybe it's a bit too narrow (which fits my preconceived ideas).

 

[Biologic]

That is true. I explain that every time it comes up.

Plants just cannot take up nearly as much CO2 as you exhale in a day, unless it is a greenhouse sort of environment. The nonmeaurement way is to just recognize that the plants need to add about as much dry mass per day by photosynthesis as you eat in dry mass (and exhale as CO2) to offset the CO2 rise.

Really makes you second guess cutting down a tree. Hahaha

Thanks for starting, and keeping going, a great thread. I agree with that statement above.

A question, that I can't seem to find the answer to: Did you ever increase the diameter of your outside air feeding line? It was raised that maybe it's a bit too narrow (which fits my preconceived ideas).

I have not run my larger skimmer line just yet. Fortunately, the skimmer line is quarter inch, so naturally I have a lot of quarter inch ro line around. I am definitely going to do this now that my skimmer is larger. The previous skimmer you could barely hear it draw in air. This larger skimmer you can hear the air being sucked in. Overall I think it’s worthwhile to run skimmer line outside. Depending on where you live, the outside air quality might be better than the indoor air quality Beyond just CO2. If it’s easy enough to do it why not? Just manage your expectations on the impact.

 

[Ashibashi]

Big relate on the tree thing! It goes so much deeper than that too - I've been reading Entangled Life by Martin Sheldrake, its about fungi and mycelium networks underground connecting trees and plants to each other. Cutting down the biggest tree in a forest is like taking google or Facebook off of the internet permenantly - theyre central hubs of movement and it throws everything into chaos getting rid of them.

Speaking of which, I've been wondering to what extent fungi play a role in a reef environment. Let me know if you guys have any references.

Great thread. I really appreciate you all sharing the knowledge. Will be following for updates!