Daily pH swing is normal, even at the Great Barrier Reef

[dz6t]

Since there are plenty of attentions to pH recently, I want to give my 2 cents regarding daily pH swing.
Coral at the Great Barrier Reef experience daily pH swing just like what happens in our reef tanks. Here is a chart of daily pH swing on the Great Barrier Reef:

 

[dz6t]

In summer, daily pH swing is from 8.12 to 8.38
In winter, daily pH swing is from 7.88 to 8.25
That is about 0.36 unit swing daily at the reef.

By the way, the average salinity of the Great Barrier reef is 35 ppt (1.026).

 

[dz6t]

Regarding coral growth related to pH, here is a study, in the graph,
“Normal pH” was maintained at 8.2
“Low pH “ was maintained at 7.9
“High pH” was maintained at 8.4

the results showed that the difference is statistically insignificant.

 

[dz6t]

In terms of coral health at different pH from 7.9 to 8.4, pH does not seem to make an impact:

 

[serwobow]

Thanks for showing this Dong. That pH swing is remarkably large on the GBR! But, also the GBR pH, even in winter is higher than my pH. Regarding the coral growth figure, was that done in ocean water, or done in a regular aquarium? I think it matters, since the ocean has way more food available for corals, and therefore, corals could adapt to a lower pH by increasing their metabolism. This may not be possible in an aquarium setting with limited food.

 

[Terry Martin]

In terms of coral health at different pH from 7.9 to 8.4, pH does not seem to make an impact:
View attachment 160457

Dong - Could you supply link to the article? Thanks

 

[dz6t]

Thanks for showing this Dong. That pH swing is remarkably large on the GBR! But, also the GBR pH, even in winter is higher than my pH. Regarding the coral growth figure, was that done in ocean water, or done in a regular aquarium? I think it matters, since the ocean has way more food available for corals, and therefore, corals could adapt to a lower pH by increasing their metabolism. This may not be possible in an aquarium setting with limited food.

The pH experiments were done in laboratory.

 

[dz6t]

Dong - Could you supply link to the article? Thanks

here is the link,
https://reefs.com/magazine/the-effect-of-ph-alkalinity-and-calcium-on-hermatypic-corals/

 

[Terry Martin]

Thanks, Dong, it's interesting to see the scientific studies. My take would be that we'll need hundreds of comparable studies to get definitive answers. This one looks quite noisy. They have 1/7 of corals die for unexplained reasons (I've been there!). They're growing them in 5 gallon tanks with hob filters so a big husbandry challenge They're testing 3 corals; 2 show stat. sig. relationship to higher ph; one doesn't. It seems most useful thing in study is sharp cut-off of corals doing worse when ca ppm goes under 370.

 

[dz6t]

You are absolutely correct that more studies with larger samples is important to see a more complete picture.

This type of controlled studies in laboratories under real world pH range are hard to find. I found some other studies that lower pH to 7.2, (a very unlikely situation in the ocean as well as in reef tanks), to compare to normal pH around 8.2, to demonstrate pH difference affects coral growth.

 

[this is me]

I don't think PH swing is an issue. I don't care for it unless it's below 7.7.

 

[Terry Martin]

Nick - Yeah, I'm just curious. We all know from experience that you can run a reef tank super successfully without worrying much about ph as long as it's in that 7.6 to 8.4 range (maybe even a tad lower) and that's what I've done for six years now. I'm just curious now as to whether running it in the 8.1 to 8.4 range is better than 7.6-7.9, and how much better. I'm inclined to believe it's better, but agnostic as to how much better. Mostly it's idle curiosity as keeping my ph probe calibrated is too much of a pain in the a** to make it worth while experimenting!

 

[dz6t]

I don't think PH swing is an issue. I don't care for it unless it's below 7.7.

Absolutely!

 

[this is me]

It might be better but if the tank set up is not naturally at those higher PH, I wouldn't bend over backward to run CO2 scrubber or anything special to get to those higher range PH. The benefit of growth is likely be offset by some other factor like lighting and flow.

 

[Terry Martin]

It might be better but if the tank set up is not naturally at those higher PH, I wouldn't bend over backward to run CO2 scrubber or anything special to get to those higher range PH. The benefit of growth is likely be offset by some other factor like lighting and flow.

true enough, many of my tank problems emerge out of some optimization project gone awry...

 

[dz6t]

Nick - Yeah, I'm just curious. We all know from experience that you can run a reef tank super successfully without worrying much about ph as long as it's in that 7.6 to 8.4 range (maybe even a tad lower) and that's what I've done for six years now. I'm just curious now as to whether running it in the 8.1 to 8.4 range is better than 7.6-7.9, and how much better. I'm inclined to believe it's better, but agnostic as to how much better. Mostly it's idle curiosity as keeping my ph probe calibrated is too much of a pain in the a$$ to make it worth while experimenting!

From limited available research data, theoretically coral will calcify slightly better when the ambient pH is higher. Coral calcification is biologically controlled inside the coral, the calcification chamber maintains its own pH value. But other factors like feeding, efficiency of photosynthesis that provides nutrients for coral, alkalinity level, calcium level, even temperature will have larger impact of coral growth. Chasing pH is not that critical for this hobby.

 

[Terry Martin]

From limited available research data, theoretically coral will calcify slightly better when the ambient pH is higher. Coral calcification is biologically controlled inside the coral, the calcification chamber maintains its own pH value. But other factors like feeding, efficiency of photosynthesis that provides nutrients for coral, alkalinity level, calcium level, even temperature will have larger impact of coral growth. Chasing pH is not that critical for this hobby.

Dong - What do you think is optimal practice in terms of feeding coral, in particular sps?

 

[dz6t]

I feed Phytoplankton, Reefroid with polyps booster, then generously feed my gang of fish with New Life Spectrum pellets. Once a while drop in some acropower when nitrate hits the bottom.

 

[FishieBusiness]

As always Dong bringing knowledge to the table. Thanks Dong!

 

[dz6t]

I bump this thread up as I get many questions regarding pH swing these days.
The Great Barrier Reef has daily pH swing just like in our tanks, so pH swing is not an issue and it does not require a solution (such as reverse light cycle on a refugium, etc).
Let it swing and don’t even worry about it.