(PH) (DO) = Calculated alkalinity?

[luisagos]

(PH) (DO) = Calculated alkalinity?

I am trying use my Controller (Profilux) to calculate alkalinity accuratel?

I can monitor continuous PH and DO with this controller.

My concern, is there any other relationship that can cause my alkalinity to be not calculated correctly?

 

[Randy Holmes-Farley]

No. You can get alkalinity from CO2 and pH, but not from oxygen. And that calculated value is likely to be less accurate than is a titrated sample.

 

[Woja222]

Would it be possible to make a chart with DO on one side and pH on the other with alkalinity in the middle and test different samples/solutions of watet to get a good baseline alkalinity? Reason I bring this up is the nightly drop in pH and rise is DO should more-or-less in turn allow the alkalinity number to remain the same. Basically just a three column chart that you connet a line from the DO to the pH...just a thought

 

[Randy Holmes-Farley]

Oxygen is unrelated to alkalinity. Just because pH rises and falls does not mean that O2 is similarly rising and falling.

For example, one can easily have a tank where O2 is saturated or even above saturation due to photosynthesis, and CO2 may also be elevated above "normal" due to elevated home air CO2 levels.

 

[Woja222]

What is the availability/pricing of a CO2 meter? Or how hard would it be to convert a pH probe into a CO2 meter? I read somewhere about that being done.

 

[Randy Holmes-Farley]

You cannot use a pH probe to measure CO2 short of measuring alkalinity.

I've not seen CO2 meters for marine use. Most are for testing air.

 

[MCsaxmaster]

I've not seen CO2 meters for marine use. Most are for testing air.

Oceanograhic instruments to measure dissolved CO2 exist (a couple of folks here have a few couple of different types--they rely on a membrane to exchange CO2 from the water and an IR sensor to examine the concentration I believe), but they'll run you $20K+. Worldwide I know of not more than a few dozen devices like this in use.

If a company comes out with a hobbyist grade 'alkalinity meter' (i.e., pH + pCO2) I can predict right now that I will trust not nearly as far as I can throw it

 

[Randy Holmes-Farley]

Thanks, Chris.

 

[luisagos]

Thank you, it was very informative thread, short live, but nevertheless very informative.

 

[Randy Holmes-Farley]

:thumbsup:

Happy Reefing.