# Ph, kh and co2...



## artemism3 (May 21, 2005)

I have a rather odd question caused by something I can't explain and have no idea as to the cause.

My tank is a 75g with tahitian sand substrate. It is moderately planted and have had Co2 running for about 6 weeks.

My tank's water is 7.5 ph when it has been outgassed with a kh of 10. My tap water after it has aged for 3 days has a ph of 8 and a kh of 10 degrees.

Why is my tank's ph lower then my tap? I have not been able to figure this out. Also considering the above, what should I be lowering my ph to with the co2 to have a healthy enviroment for my fish?

Thank you!

Jeremy


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## MatPat (Mar 22, 2004)

How do you outgas the CO2 out of your tank? Unless you went more than overnight without adding CO2 I would think there would still be residual CO2 in the tank. 

A pH of 7.0 would give you 30ppm of CO2. I would probably get your pH to 7.0 and SLOWLY adjust it higher. A drop in pH to 6.9 in your case gives you 38ppm of CO2. 40ppm has been suggested to be the lethal range for fish but I keep mine much higher than that.


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## artemism3 (May 21, 2005)

Matt,

Thanks for the response.

The water I checked as being outgassed was removed from the tank on Monday and set aside for this reason.

My main concern is this...with a ph of 7.5 and 10 degrees kh, my tank with no additional Co2 somehow has aobut 10ppm of co2. Is this too much in a non Co2 injected enviroment? I am really concerned about this extra 10ppm of Co2 which I can't explain...

Should I be?


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## MatPat (Mar 22, 2004)

Do you have any driftwood in the tank or did you use peat under the sand or in your filter? Driftwood or peat will cause the pH to drop. A very dirty filter or decaying plant matter in the tank can also cause a drop in pH. 

10ppm of CO2 will not cause any problems with fish. I wouldn't be concerned with 10ppm of CO2.


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## artemism3 (May 21, 2005)

no driftwood or the like yet....

I guess it could be from decaying plant material...I rescaped the whole tank last saturday and tried to eliminate as much decayed stuff as possible.

So with this in mind...should I shoot for 30ppm above and beyond the 10ppm that supposedly exists, or should I include that value in my calculation and only add 20ppm extra?

Thank you sooo much Matt! I greatly appreciate your time!

Jeremy


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## MatPat (Mar 22, 2004)

I see why you are worried about the 10ppm now  Don't worry and add enough CO2 to get to 30ppm. As long as you just worry about the total number it doesn't matter what was there before and what you add.


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## artemism3 (May 21, 2005)

So I should try and get my ph to 7, which would then have me at 30ppm total, right?

Thank you Matt for aleviating my confusion!


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## MatPat (Mar 22, 2004)

You are more than welcome. 

With a pH of 7.0 and a KH of 10 you should have 30ppm of CO2


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