Planted Tank Guru
Join Date: Mar 2014
Location: Ontario, Canada
So just so I am clear, the chart tells us roughly what the amount of co2 should be a any given kh and ph value. The original ph shouldn't matter that much then either right? As long as you kh is accurate you can just follow the line over.
I took some time last night to do some testing on a few different water samples. One from my main tank, one from my degassed tap water, and one from another tank (30g).
I tested all the kh and ph values of each sample and the lh was all the same. Ph differed which was to be expected. To fully offgas any sample was near impossible. Highest I could get the ph was 8.3. I off gassed by putting the samples into large buckets and swirled and shakes them water the ph change higher and higher as I did this.
My conclusion is that all of my samples in terms of kh are constant and don't vary more than 1/2 a degree. Also, the 1 point drop I was told to achieve is not entirely the best suggestion. I think its more important to look at your kh value and follow that over till you find what level of co2 you wish to obtain. Then monitor the ph till you are able to consistently reach that level.
In my case, with a kh with 9, my desired ph would be 6.9-7. This puts my co2 at 29-36ppm.
In my case I don't really have anything in my tank that would alter the ph in a way that would make my values skewed. Its important to look at each tank case by case.
75 Gallon Low Tech w/ Green Terror Pair