Would a Constant pH (8.3) be Beneficial to (SPS) Coral Growth?

[Dr. Jim]

It is well-accepted that corals (SPS, in particular), grow faster at a higher pH (8.2-8.3 compared to 7.8) (assuming other parameters are kept optimal) and that stability is one of the main "keys" to successful coral growth. Can that "stability" be extended to pH? In other words, would it be beneficial to maintain pH at a constant level (8.2 or 8.3) rather than allowing the more "normal" diurnal fluctuation? …..and, what would that ideal pH be? (Let's disregard the effort/difficulty involved in keeping the pH constant).

Obviously, aquarists have had much success with growing corals over the decades with allowing "normal" diurnal fluctuation of pH, but my question is: Would a constant pH be even MORE beneficial, or would it be more likely to be harmful? I know it has been suggested that different organisms/(corals) may prefer different pH's, but if my concern is only with SPS, I'm wondering if a constant pH of 8.3 would be harmful or beneficial.

I've devised a way to maintain a constant pH of 8.3 by plumbing and controlling 3 tubes to my skimmer:
1) Room air (High CO2)
2) Outside air (Low CO2)
3) Outside air with CO2 scrubber (Very Low CO2).

At the present time, since I'm trapped at home because of Covid and have time on my hands, I'm controlling the 3 inputs with manual valves ("by hand") throughout the day but have 2 motorized ball valves arriving soon. At the moment, I'm maintaining the pH most of the time right at 8.3 but with occasional fluctuations between 8.27 and 8.34. Once I get the motorized ball valves and with the help of my GHL Controller, I expect to be able to maintain the pH 8.3 with a 0.05 hysteresis, so, 8.28-8.33. (I may discuss the details of this set-up at a later date on a different Forum since such a discussion would be more appropriate for a DIY Forum rather than Randy's Chemistry Forum).

So, I would welcome any suggestions or responses to my questions above (in bold print). It might be helpful to state whether your replies/opinions are based on scientific literature or anecdotal, when appropriate.

Thanks for helping!

 

[kyleinpdx]

I cant imagine it would be harmful, I dont know of any biological processes that require lower ph or ph fluctuations.

Many people, myself included run a reverse light cycle on their refugiums to regulate ph when the main display lights are out. For example, my day time ph is around 8.4 - 8.5 and my night time ph is between 8.25 and 8.3. Once I get my cheato and caulerpa growing a bit more I'll be shooting for 8.3+ at night.

 

[chema]

I'm glad you have set up a system to address this question as it is something I have been thinking about. The air line to my skimmer takes fresh air from outside and goes through a CO2 scrubber before entering the air intake of the skimmer. I was figuring out a system based on solenoid valves and controlled by Profilux to alternate outside-CO2 scrubber air and room air aiming at a stable pH. However, the solenoid valves I have found are the ones used for CO2 lines. They are too narrow to fit the tubes I'm using now.

I'll be very interested in your results. Please, keep us informed on the progress.

 

[Randy Holmes-Farley]

There is no perfect answer at the moment, but this current thread has a lot of discussion on this topic:

Alkalinity stability? pH stability? Are they even different?

It is currently the dogma of the reef aquarium hobby to say that alkalinity stability is very important for SPS corals, and that pH is not. Often, the very idea of someone trying to optimize pH is called “chasing numbers” as if that statement by itself shows it to be foolish. Since I have...

www.reef2reef.com

 

[Dr. Jim]

There is no perfect answer at the moment, but this current thread has a lot of discussion on this topic:

Alkalinity stability? pH stability? Are they even different?

It is currently the dogma of the reef aquarium hobby to say that alkalinity stability is very important for SPS corals, and that pH is not. Often, the very idea of someone trying to optimize pH is called “chasing numbers” as if that statement by itself shows it to be foolish. Since I have...

www.reef2reef.com

I have seen that thread, and thank you, again, Randy. In your first post you wrote,
"Perhaps folks with an experimental bent might consider “chasing pH” or “chasing stable pH” while also maintaining stable alkalinity to see if it has benefits." Well...it seems that this is exactly what I'm looking to do. So far, I'm very confident that I will be able to hold the pH constant, but still need to work on Alk control.

One change I'm making already is to target pH 8.25 (instead of 8.3 as I wrote above), at least temporarily. (My main reason is because I noticed one SPS frag today losing some tissue and am concerned that perhaps there has been too sudden a change in pH in just the last week or so). Trying to pick the correct pH to target seems confusing. BRS's study showed that corals grew faster at pH 8.3 compared to 7.8.....but it would have been nice if they made comparisons to 8.1 and 8.2 as well. Some, like Xero and kleinpdx, are having success at pH 8.4ish. But Lasse feels that the "sweet spot" is between 8.1-8.2. I will randomly choose 8.25 for now.....we'll see how that goes.

 

[blasterman]

It's possible that diurnal pH fluctuations can cause stress on SPS, and this would give credence to our experience that large tanks tend to handle SPS growth over the long term better than smaller tanks. The larger tank will have a much larger capacity to hold carbonic acid (C02) fluctuations down.

Corals need high pH levels because their growth tissues export protons and create a narrow area of high pH which causes precipitate to form and be used as skeletal material. lower environmental pH makes it difficult to maintain this barrier. Just read a neat article how a big coral propagator in Florida uses massive amounts of calcium hydroxide tp keep a pH as close to 8.5 as possible. Then again I've seen many reactor driven SPS tanks with crazy growth that never go north of 8.0.

My own intuition is that there are more factors that can inhibit that proton export than just C02. reactor driven tanks are proof of this.

 

[chema]

It is well-accepted that corals (SPS, in particular), grow faster at a higher pH (8.2-8.3 compared to 7.8) (assuming other parameters are kept optimal) and that stability is one of the main "keys" to successful coral growth. Can that "stability" be extended to pH? In other words, would it be beneficial to maintain pH at a constant level (8.2 or 8.3) rather than allowing the more "normal" diurnal fluctuation? …..and, what would that ideal pH be? (Let's disregard the effort/difficulty involved in keeping the pH constant).

Obviously, aquarists have had much success with growing corals over the decades with allowing "normal" diurnal fluctuation of pH, but my question is: Would a constant pH be even MORE beneficial, or would it be more likely to be harmful? I know it has been suggested that different organisms/(corals) may prefer different pH's, but if my concern is only with SPS, I'm wondering if a constant pH of 8.3 would be harmful or beneficial.

I've devised a way to maintain a constant pH of 8.3 by plumbing and controlling 3 tubes to my skimmer:
1) Room air (High CO2)
2) Outside air (Low CO2)
3) Outside air with CO2 scrubber (Very Low CO2).

At the present time, since I'm trapped at home because of Covid and have time on my hands, I'm controlling the 3 inputs with manual valves ("by hand") throughout the day but have 2 motorized ball valves arriving soon. At the moment, I'm maintaining the pH most of the time right at 8.3 but with occasional fluctuations between 8.27 and 8.34. Once I get the motorized ball valves and with the help of my GHL Controller, I expect to be able to maintain the pH 8.3 with a 0.05 hysteresis, so, 8.28-8.33. (I may discuss the details of this set-up at a later date on a different Forum since such a discussion would be more appropriate for a DIY Forum rather than Randy's Chemistry Forum).

So, I would welcome any suggestions or responses to my questions above (in bold print). It might be helpful to state whether your replies/opinions are based on scientific literature or anecdotal, when appropriate.

Thanks for helping!

What kind of motorized valve balls do you intend to use?

Thank you

 

[Dr. Jim]

What kind of motorized valve balls do you intend to use?

Thank you

I plan to start a new thread in a "DIY Forum" at some point since we are drifting from a "chemistry topic" in Randy's forum, but for now....

Here are the two (3/4") I ordered. I ordered the stainless steel but they also come in brass (at half the price). I doubt there will be any metal leaching into the air but I decided not to take any chances. Stainless steel is mostly iron (with a little chromium). Brass is mostly copper (with a little zinc). If one of them was to "leach" I would rather it be the iron. I'm also passing the air thru carbon as an extra precaution.
I am no expert with these items, but I believe "motorized ball valves" may be more ideal than solenoids. (Perhaps someone with more knowledge can chime in here). With the "motorized ball valve", after the activation the power cuts off (so there is no heating or constant current). With a solenoid, there is constant current while the unit is being energized.





Hope this helps.

 

[kyleinpdx]

Since I was thinking about this thread, I snapped a picture:

(please excuse the grime & duct tape I'm mocking up a controller board with corrugated plastic sheet)

I run LEDs and T5's, LEDs come on 1.5hrs before first T5's and run throughout the day, 2x T5 run for 6hrs, 4x T5 run for an hour at noon, then LEDs are on for another few hours after the T5's go out. So I still have a few hours of high quality photosynthesis that'll bump those numbers up a bit more.

I could absolutely be off 0.05 or so, but I doubt much more than that. Its a pinpoint marine ph probe that was calibrated about 5 months ago and is less than a year old. I'll probably calibrate it again when it gets to 6-7mos since the last time.

I realize this isnt exactly the topic of your thread but I bring it up because I imagine you are going to have a hard time locking that ph number in. Adjustments both upwards and downwards have a lot of "elasticity" in them, and by that I mean you have to provide the input (either o2 rich air or a reduction in aeration/oxygenation in the event you want to drive ph down) and wait for it to buffer/deplete before your measurements will show any change.

 

[huckilt]

I can only speak from my experience and say that my ph stays at a constant 8.3 day and night and though I’ve only got two frags a Xenia and a hammer coral they’ve had a few run ins with problems all of which I’m assuming stemmed from having a brass check valve on the system but through all the problems they’ve always bounced back rather quickly from almost completely shriveled up and retracted to fully “inflated “ and pulsing again within a week and showing new growth after the 2nd. And all I do is add top off water with diy alkalinity 2 part in a slow drip and add some calcium once a week and magnesium when tests show I need some I test magnesium every two weeks lately the temp has been fluctuating from 77-80 from day to night but I live in the desert where it’s still a bit hot in the day but gets down to just above freezing at night once it’s cold all day I’m sure it will stabilize again but as long as I keep up with my “regimen” them two lil frags are happy happy happy

 

[Dr. Jim]

How do you keep your pH during the night at the same level during the day?
How are you measuring it? (with a Controller? If so, I'd love to see a 24hr graph)

If they bounce back from your "corrections" it seems unlikely the brass check valve would be the culprit.

Glad your corals are happy!

 

[EMeyer]

Some will find me a broken record on this subject but thats OK. I wish to remind the reader that daily cycles in pH are a natural feature of coral reefs

these are not artificial features of aquariums. These are natural features of marine habitats including coral reefs. Notice that many coral reefs barely exceed 8, ever, and spend a lot of time below 8. Not one of them ever touches 8.3.
[reference is here]

But somehow the reef keeping hobby got this idea in its head that stable 8.3 would be preferable... why?

In fact, experiments comparing calcification rates under variable pH versus stable pH showed that variable pH promotes greater calcification rates (light blue box in the following figure)

[reference here]

As far as I can tell, hobbyists are misguided by chasing unnaturally high and stable pH. Corals don't encounter those levels in nature, and they grow faster with variable than stable pH, as the experiments linked above showed.

I think our corals would do best if we tried to mimic the environment they evolved in over the past several tens to hundreds of millions of years rather than imposing artificial conditions like stable pH or high alkalinity.

 

[Dr. Jim]

daily cycles in pH are a natural feature of coral reefs

In fact, experiments comparing calcification rates under variable pH versus stable pH showed that variable pH promotes greater calcification rates (light blue box in the following figure)

As far as I can tell, hobbyists are misguided by chasing unnaturally high and stable pH. Corals don't encounter those levels in nature, and they grow faster with variable than stable pH, as the experiments linked above showed.

I think our corals would do best if we tried to mimic the environment they evolved in over the past several tens to hundreds of millions of years rather than imposing artificial conditions like stable pH or high alkalinity.

I rather quickly abandoned my experiment to attempt to maintain a constant pH. One of the main reasons was, as EMeyer stated, "daily cycles in pH are a natural feature of coral reefs". I agree that it doesn't make sense that all corals will prefer the same pH, and if they do, how do we know what that pH is?

However, I haven't seen studies that show that calcification is more efficient at the lower pH range, so I still use simple features to raise the pH, like outside air piped to my skimmer and kalkwasser additions at night, but with diurnal fluctuation.

(One of the main reasons, (and perhaps a foolish reason), for me to pursue this experiment was because, at the time, I had a recently purchased GHL Controller system and I just wanted to play with the Programmable Logic to see if I could do it).

 

[Randy Holmes-Farley]

Some will find me a broken record on this subject but thats OK. I wish to remind the reader that daily cycles in pH are a natural feature of coral reefs

these are not artificial features of aquariums. These are natural features of marine habitats including coral reefs. Notice that many coral reefs barely exceed 8, ever, and spend a lot of time below 8. Not one of them ever touches 8.3.
[reference is here]

But somehow the reef keeping hobby got this idea in its head that stable 8.3 would be preferable... why?

In fact, experiments comparing calcification rates under variable pH versus stable pH showed that variable pH promotes greater calcification rates (light blue box in the following figure)

[reference here]

As far as I can tell, hobbyists are misguided by chasing unnaturally high and stable pH. Corals don't encounter those levels in nature, and they grow faster with variable than stable pH, as the experiments linked above showed.

I think our corals would do best if we tried to mimic the environment they evolved in over the past several tens to hundreds of millions of years rather than imposing artificial conditions like stable pH or high alkalinity.

The pH in reef tanks is frequently far below what happens naturally, and “chasing pH” as you put it would seem to be exactly what you are espousing in maintaining natural levels. Yet you don’t recommend that? Why not?

 

[Randy Holmes-Farley]

I rather quickly abandoned my experiment to attempt to maintain a constant pH. One of the main reasons was, as EMeyer stated, "daily cycles in pH are a natural feature of coral reefs". I agree that it doesn't make sense that all corals will prefer the same pH, and if they do, how do we know what that pH is?

However, I haven't seen studies that show that calcification is more efficient at the lower pH range, so I still use simple features to raise the pH, like outside air piped to my skimmer and kalkwasser additions at night, but with diurnal fluctuation.

(One of the main reasons, (and perhaps a foolish reason), for me to pursue this experiment was because, at the time, I had a recently purchased GHL Controller system and I just wanted to play with the Programmable Logic to see if I could do it).

Why assume that exactly matching the natural environment is optimal? Acceptable, certainly. Optimal? That needs evidence.

 

[Dr. Jim]

Why assume that exactly matching the natural environment is optimal? Acceptable, certainly. Optimal? That needs evidence.

I didn't say anything about matching the natural environment. I'm just suggesting that it may be safer to follow a natural diurnal variation rather than maintaining a constant pH which hasn't been much studied/tested.
Also, the pH of the ocean "today" is lower than it was years ago due to acidification, so trying to match the current (lower) pH may not be what corals really "prefer." (That would further support the idea that a higher pH range, perhaps 8.2-8.4, is more beneficial than a lower range).

 

[Randy Holmes-Farley]

I didn't say anything about matching the natural environment. I'm just suggesting that it may be safer to follow a natural diurnal variation rather than maintaining a constant pH which hasn't been much studied/tested.
Also, the pH of the ocean "today" is lower than it was years ago due to acidification, so trying to match the current (lower) pH may not be what corals really "prefer." (That would further support the idea that a higher pH range, perhaps 8.2-8.4, is more beneficial than a lower range).

I was addressing EMeyers comment to you, not your comment.

 

[Cole.mormon]

Comstant ph?

 

[Cole.mormon]

Yes it will help alot

 

[EMeyer]

The second study I linked above (https://www.sciencedirect.com/science/article/pii/S0022098118300327), showed specifically that fluctuating pH (i.e. following natural daily cycles in pH) promotes faster growth.