Measuring Co2

[newfishaddict]

Hi, I don’t understand kh and ph and how they relate to dissolved co2. Is the co2 calculated an approximation? If it is an approximation then I do understand however if it is not an approximation it does not make sense to me. For example, If I add co2 to my tank the pH will go down, if I add bogwood to my tank the pH will also go down; certainly the bogwood will not add co2 to the water, but according to the kh and ph cross reference tables any drop in ph correlates to a rise in co2....

Can anyone explain?

 

[zig]

The bogwood contains natural acidic tannins this is why it lowers the Ph, when you add co2 you are adding another acid this time carbonic acid..........as you acidify water the Ph will drop, for instance acid rain will have a very low Ph, also vinegar or lemon juice would have extremely low Phs probably as low as Ph 1 or 2....the KH is the carbonate hardness or temporary hardness of water, it is really the buffering capacity to try and neutralise the acidic effects of water without major changes to Ph, the higher the KH the higher the buffering capacity and the less likely that your will get Ph swings particularily as you inject CO2.

Another acid that is ofton overlooked that also has an effect on Ph is nitric acid (nitrate) this will also drop your Ph over time particularily if your KH or buffering capacity is very low, aquariums with a low KH and high nitrate levels should have regular water changes in order to limit this effect on the Ph.

Anyway i hope that makes some sense..........

 

[newfishaddict]

The bogwood contains natural acidic tannins this is why it lowers the Ph, when you add co2 you are adding another acid this time carbonic acid..........as you acidify water the Ph will drop, for instance acid rain will have a very low Ph, also vinegar or lemon juice would have extremely low Phs probably as low as Ph 1 or 2....the KH is the carbonate hardness or temporary hardness of water, it is really the buffering capacity to try and neutralise the acidic effects of water without major changes to Ph, the higher the KH the higher the buffering capacity and the less likely that your will get Ph swings particularily as you inject CO2.

Another acid that is ofton overlooked that also has an effect on Ph is nitric acid (nitrate) this will also drop your Ph over time particularily if your KH or buffering capacity is very low, aquariums with a low KH and high nitrate levels should have regular water changes in order to limit this effect on the Ph.

Anyway i hope that makes some sense..........

I understand all that chemistry but; I am asking about the method used to calculate co2, using a chart and how Ph and kh relate to each other. This suggests to me that if I lower my ph using some method other than co2 injection that I would calculate more c02 in the water, this does not make sense to me…

 

[zig]

Ph KH and CO2 have a fixed relationship as long as carbonate is the only buffer present.

 

[newfishaddict]

Ph KH and CO2 have a fixed relationship as long as carbonate is the only buffer present.

Thanks so much, that is EXACTLY what I wanted to know.