How true is this ADA statement?

[Tom]

How true is this statement from the online AquaJournals?

It is safer initially to judge if the CO2 concentration is appropriate or not by measuring changes in pH. When CO2 is added to water, pH level decreases. As CO2 is consumed by the photosynthesis of aquatic plants, the pH value rises. Provided that the water quality of the original water is neutral (near pH 7.0), if the water becomes slightly acidic (pH 6.8 to 6.6) with CO2 injection while aquatic plants are vigorously photosynthesizing, you can consider the CO2 level is adequate. I hope you can now grow healthy aquatic plants by maintaining a proper CO2 level.

From this, I understand that if the pH of the water drops during photosynthesis then there must be enough CO2 as the level of CO2 being injected is greater than that which is being used by the plants. This is assuming it's the carbon that's causing the drop. Is this a sensible or reasonably accurate way to determine CO2 levels as opposed to having a drop checker in the tank constantly? I'm assuming even though Aquasoil reduces pH, it won't have a dramatic enough effect to give false results for this test?

Cheers,
Tom

 

[George Farmer]

I don't really understand it. Perhaps it's a poor translation.

I'd say measuring pH is not a very accurate way to measure CO2, especially in a tank with a substrate that both reduces and buffers pH...

Why are you asking? CO2/algae issues?

 

[bigmatt]

Statement is chemically accurate - if you're adding co2 to pure RO! But who does that!!!!????!! For a fish tank maintained with tap/remineralised water, rocks, wood etc it's pretty meaningless. i don't really understand the obsession with pH - co2 DOES change pH, but so do a whole host of other variables!M

 

[Tom]

George - they are assuming that if the pH still goes down while the plants are using the CO2, then there must be more than enough. As you and Matt both point out there are too many variables, especially with their substrates. But then surely the substrate won't have that acute an effect as to alter the pH noticably through one day?

The reason I was asking is that I was confused about why I was still getting CO2-related algae while injecting what I thought was way overkill + liquid carbon. I was thinking that if their statement is accurate enough, then if I saw a decrease in pH during the day, then I could eliminate CO2 injection as my issue.

These last couple of days though I've seen improvements, so am just waiting to see if the good signs continue Might throw in some more Amanos soon too.