Raimeiken
Aquarium Advice Activist
Would you need a CO2 system if your water has a PH of 6.9 and a KH of 7? Because when i look at those chart thingies, a ph of 6.9 and a Kh of 7 is already about 20-25+ ppm. :?
I'm a little confused, Q about CO2
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Mr Burns
Aquarium Advice FINatic
did you add anything to your water to bring it down to 6.9, or is that the pH of standing tap water?
_Nemo_
Aquarium Advice Apprentice
How do you achieve this balance? With a kH=7, the pH should be in the vicinity of 8. More details please.
Mr Burns
Aquarium Advice FINatic
Raimeiken
Aquarium Advice Activist
ok , i only used that for an example. Is the co2 system only used for lowering thw ph? actually my tap water is 7.6 somethimes 7.8 ph and kh is 7.
Mr Burns
Aquarium Advice FINatic
that's not the only reason for using co2, but that is one of the inherent (sometimes good) side effects. that's why it is good to keep your buffering capacity up -either from hard tap water or something like crushed coral in a filter- so you don't have huge pH swings that could trigger something that would stress your fish. that is, of course, unless you have fish that prefer soft water...that's a whole 'nother can of worms...
i don't know exactly, but my (fairly educated) guess is that tap water has very little co2 in it, even less once it gets dumped into your tank and mixed around. in that particular situation i don't think the chart is of any use. hence, the need for injection methods. hopefully somebody else can back that up...
i don't know exactly, but my (fairly educated) guess is that tap water has very little co2 in it, even less once it gets dumped into your tank and mixed around. in that particular situation i don't think the chart is of any use. hence, the need for injection methods. hopefully somebody else can back that up...
jsoong
Aquarium Advice Addict
If the water is not "doctored", your KH consists of mostly bicarbonates. There is a fixed relationship between CO2 level, bicarbonates & pH. Assuming that your water is equilibrated with air, & there is no injected CO2, the CO2 in the tank MUST be approx. 3 ppm. With a KH of 7, the pH should be 7.6 or so.
When you test the water & the measured KH & pH don't give a normal atmospheric CO2 level, 2 things can be true:
1. You have excess CO2 in water (this is often seen in well water), in that case the CO2 will escape & the pH will rise over 24 Hrs or so to the theoretical value.
2. The KH is NOT all bicarbonates - eg. there is nitrates, phosphates or other buffers in the water, or you have added pH down, etc. In that case you cannot use any of the KH/pH/CO2 calculators on the net - as all of them calculates CO2 levels assuming that the KH is 100% bicarbonates.
When you have a mixed buffer situation, the only way to know the CO2 level is to measure it directely. (I am not sure of the CO2 test kits on the market - if they actually measure CO2 directly or indirectly. I normally measure CO2 using infared absorption &/OR Mass Spectrometry.)
When you test the water & the measured KH & pH don't give a normal atmospheric CO2 level, 2 things can be true:
1. You have excess CO2 in water (this is often seen in well water), in that case the CO2 will escape & the pH will rise over 24 Hrs or so to the theoretical value.
2. The KH is NOT all bicarbonates - eg. there is nitrates, phosphates or other buffers in the water, or you have added pH down, etc. In that case you cannot use any of the KH/pH/CO2 calculators on the net - as all of them calculates CO2 levels assuming that the KH is 100% bicarbonates.
When you have a mixed buffer situation, the only way to know the CO2 level is to measure it directely. (I am not sure of the CO2 test kits on the market - if they actually measure CO2 directly or indirectly. I normally measure CO2 using infared absorption &/OR Mass Spectrometry.)
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