Re: [APD] CO2 and pH control

[Gordon and Susan Watkins <gwatkins at ritternet_com>]

My resting tap water now shows 8.6. I'm not sure why I previously tested 
at 9.3. My tank has a laterite sublayer with "inert" aquarium gravel on 
top. Decorations are petrified wood. Trickle filter has a floss 
prefilter and bioballs.

Jerry Baker wrote:

>Gordon and Susan Watkins wrote:
>  
>
>>The pH reading is coming from the sump of my trickle filter using a 
>>Milwaukee controller. Right now, with CO2 running, it shows 8.1. I 
>>checked another tank which has been set up continuously for over 25 
>>years and, using the same electrode, it showed 8.9. What else could 
>>account for the discrepancy?
>>    
>>
>
>You could have gravel or decorations which are buffering your pH. Things 
>like shells, coral, limestone, marble, etc. will do that.
>
>I intended to ask what is the pH of the tap water after it has sat out 
>for awhile (not in an aquarium).
>
>  
>
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