CO2 and effects on pH

[jcreefer]

Just to show everyone cause and effect of level of CO2 and pH.  I do not have a CO2 meter for measurement, so I can't provide empirical values and I am only providing a generalized data.  

 

If people are curious about CO2 and pH relation, I think Randy Holmes-Farley's articles would be a good read: Reefkeeping - Low pH: Causes and Cures

 

One of the ways to combat low pH, caused by elevated CO2 levels is to open up windows to allow air to circulate and dilute high CO2 levels that build up indoors.  The other method is the use of CO2 scrubbers, which uses lime soda to absorb CO2, and is commonly attached to the inlet of your skimmer.  

 

Why chase pH?  I thought people say it's not important?

While it is not as important as say Alk, generally speaking, it is true we don't need to hit a specific target.  While pH is often determined by your salt mix and your CO2 level (and by extension, your O2 level) there are anecdotal evidence and factors that striving for a higher pH lends to "better" growth and therefore coral health and coloration.  Thus you often see and hear aquarists strive for higher pH levels, targeting a range of 8.1-8.3 (or 8.4).

 

For my 30L, I have a BRS CO2 scrubber, using the Two Little Fishes CO2 media, attached to my AquaMaxx WS1 skimmer.  As you can see, with the windows open, pH levels range from ~8.12-8.40 on a daily basis, an approximate 0.28 swing.  Due to the Glass Fire raging in the North Bay, we've had to once again (this is the third time since Aug 17th to be exact) had to close our windows due to poor air quality (AQI PM2.5 ~ 200 as I am typing).  As you can see, with the window closed, my pH now is at ~8.08 - 8.28, a range of 0.20.  

 

In case you're wondering, prior to the CO2 scrubber, my pH ranged around 7.90-8.10 with windows closed

To summarize

CO2 scrubber installed/windows open: 8.12-8.40

CO2 scrubber installed/windows closed: 8.08-8.28

No CO2 scrubber installed/windows open: ~7.90-8.10

No CO2 scrubber installed/windows closed: ~7.70-7.90

 

 

 

-Jeff

[mcarroll]

On 10/2/2020 at 11:44 AM, jcreefer said:

Why chase pH?  I thought people say it's not important?

While it is not as important as say Alk, generally speaking, it is true we don't need to hit a specific target.  While pH is often determined by your salt mix and your CO2 level (and by extension, your O2 level) there are anecdotal evidence and factors that striving for a higher pH lends to "better" growth and therefore coral health and coloration.  Thus you often see and hear aquarists strive for higher pH levels, targeting a range of 8.1-8.3 (or 8.4).

Very interesting experiment!  But I think the question still stands.  Why chase pH?  Pick any nice tank that doesn't chase pH as a counter example.

 

On 10/2/2020 at 11:44 AM, jcreefer said:

CO2 scrubber installed/windows open: 8.12-8.40

CO2 scrubber installed/windows closed: 8.08-8.28

No CO2 scrubber installed/windows open: ~7.90-8.10

No CO2 scrubber installed/windows closed: ~7.70-7.90

The truth is that none of those values are very low...even "no scrubber/windows closed".  Lots of really nice reefs run in that same pH range.  I don't test pH, but I bet my reef runs at pH 7.7-7.9 too.

 

I'm already well-documented in this thinking and even I just got wow'd by this 2020 aticle I just found in this "Bulletin of Marine Science" article:

 

Pacific-wide pH snapshots reveal that high coral covercorrelates with low, but variable pH

 

Yes, you have permission to be surprised as the researchers were:

 

High amounts of coral cover are correlated with LOW PH!

 

This is an open-access article, so the full PDF is available – please check it out!