# confused about ph, kh and co2



## neil (Apr 10, 2004)

Hi guys,

I was wondering if someone could clarify the whole ph kh co2 mg/l relationship. 

According to denerelle (sp) and their co2 chart my tank has 13mg/l co2, with the ph being 7 and the kh at 4. 

Now really they recommend with the ph at 7 a kh of 6 to give me 20mg/l

or a ph of about 6.8 and a kh at 4 to give me 20mg/l

so I either raise the kh or lower the ph right? What's the best way to go, I could buffer the kh with bicarbonate of soda but wont this also raise the ph? The only other thing I can think of doing is increasing the co2 to lower the ph. Is this right??


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## dennis (Mar 1, 2004)

You are right. You must raise you CO2 level. Raising the kH with bicarb will only raise the pH along with it. You can raise the pH with either a Pressurized setup or with DIY Both these links come from Bob Alston's web page. A great resource for CO2 information. You also might want to try for CO2 levels of 25-30ppm. Just remember that with improved CO2 comes improved photosynthesis and growth rates, therefore causing the need for more water column fertalization.

Hope this helps


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## niko (Jan 28, 2004)

Neil,

Yes, use CO2 to raise the Co2 concentration.  

But something that you may not know is that you don't need to nail the CO2 concentration at 20 exactly. It can be much more than the suggested range of 20-30. A concentration of 60, 80, or even higher does not harm the fish if the plants grow well.

--Nikolay


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## dennis (Mar 1, 2004)

Nikolay is right, however be vey careful. This only is safe if you have lots of plants growing very well. Aside form that, plants reach CO2 saturation, the point where extra ia just waste, at around 30ppm

Hope that helps


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## neil (Apr 10, 2004)

Hi guys, 

Thanks, yes I'm using pressurised co2, I will check out the links. 

I know kh is the buffering capacity so I guess I will have to keep an eye on the ph more to prevent swings in the readings.


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