Kh and CO2 relation....

[t3r]

Hi all...i've recently tested the amount of dissolved CO2 in my tank and the reading was 20mg/l but the bubbles in the bubble counter are coming out at an uncountable rate.My dKh is ard 5 to 6.Does the hardness of water affect how much CO2 get dissolved?

[PeterGwee]

Nope. Its the way the CO2 is mixed that determines how well the CO2 dissolve.

[Allen_1971]

KH is a measure of carbonate hardness in the water. Carbonates in the water form an acid buffer. An acid buffer is something which resists the change of PH to acidic level (<7). CO2 on the other hand when dissolved is acidic. Dissolve enough of it, and your water becomes more acidic.

So assuming that carbonates in your system (measured as KH) are the only acid buffers present, and dissolved CO2 is the only substance influencing the acidity of the water, then by measuring your PH, and knowing your KH, a direct relation can be drawn as to how much CO2 is in your system.

Here is a link for such a chart

http://www.thekrib.com/Plants/CO2/co2-dietsch.gif

Alternatively, there are online calculators which work on the same basis... and heres a link to one

http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm

In short though, the hardness itself does not influence how fast CO2 dissolves (as peter mentioned). But the harder your water, the more CO2 has to be dissolved to achieve the same PH shift.

[t3r]

Ok got it,thanks Peter and Allan for sharing ya knowledge.Anyway are CO2 test kits more accurate or is the comparing Ph and Kh menthod to get a CO2 reading more accurate??