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AndyT. · 12-21-2006, 07:56 AM

Well, think of it this way...

Overnight the plants release CO2 and consume O2... CO2 being acidic, this means that the pH should have dropped over the night.

During the day this reverses, with the plants consuming CO2 and producing O2. If you don't supplement CO2 the normal cycle would be for the morning to be the time with the lowest pH, just before lights come on. The pH should rise throught he day as the CO2 in the aquarium is utilized by the plants.

Back to what Amano says - I think he is indicating that an increase in pH would show that CO2 is being depleted in the aquarium faster than it is being replaced. So any increase would indicate that there is not enough CO2 supplementation (if you assume that the early morning CO2 and pH levels are ideal).

The pH scale is logarithmic and if I recall correctly (always a problem) each 0.1 change represents a 10x change in pH. A change from a pH of 8 to 7 is a 100x change.

So I would go for a decrease in pH of about 0.2 to 0.4 as being okay and anything larger indicating too much CO2 is being added. But that is just my take on it.

The much discussed drop checker is an easy way to use pH to monitor CO2 levels.

12-21-2006, 07:56 AM	#3 (permalink)
AndyT. Senior Member Join Date: Jun 2006 Location: Dallas, Texas Posts: 175 iTrader Ratings: 0 Plant Points: 15960	Well, think of it this way... Overnight the plants release CO2 and consume O2... CO2 being acidic, this means that the pH should have dropped over the night. During the day this reverses, with the plants consuming CO2 and producing O2. If you don't supplement CO2 the normal cycle would be for the morning to be the time with the lowest pH, just before lights come on. The pH should rise throught he day as the CO2 in the aquarium is utilized by the plants. Back to what Amano says - I think he is indicating that an increase in pH would show that CO2 is being depleted in the aquarium faster than it is being replaced. So any increase would indicate that there is not enough CO2 supplementation (if you assume that the early morning CO2 and pH levels are ideal). The pH scale is logarithmic and if I recall correctly (always a problem) each 0.1 change represents a 10x change in pH. A change from a pH of 8 to 7 is a 100x change. So I would go for a decrease in pH of about 0.2 to 0.4 as being okay and anything larger indicating too much CO2 is being added. But that is just my take on it. The much discussed drop checker is an easy way to use pH to monitor CO2 levels.