GardenBanter.co.uk - View Single Post

12-01-2006, 03:36 PM posted to rec.aquaria.freshwater.plants

wrote:

While I was looking at the usual chart relating KH - pH - CO2
I found that if I wanted a 'target' CO2 level of 15mg/l this always
resulted in a drop of pH of about 0.7 from the no-CO2 equilibrium
(atmospheric) level of 3mg (is that right ?) to the pH at the 15mg injected
level, for all KH values between 1 and 8
sorry for poor english, did that make sense ?

Doing the same for a target of 25mg the ph drop needed was 0.9 for all/any
KH water.

Similar, for a target level of 30mg/l required(resulted in) a drop of about
1.0 in the pH for all KH waters from KH=1 to KH=8 (ie. all the KH's that I
examined )

In other words, I dont need a KH test kit, all I need is a pH test
measuring the non-carbonated water and the carbonated(injected) water.

Am I losing my marbles, I've not seen any refs. on the internet to this,
they all require me to test the KH to know the mg CO2
What am I missing ?

I only use a pH meter to determine the levels of CO2 in my aquariums at
any given moment. The KH is usually a constant, so you only need to ever
measure that once, unless you are producing your own KH level from a
reverse osmosis filter or rain water. Actually, it is sometimes possible
for KH to vary from your tap, especially if you live in a hot and dry
region. The water authorities will sometime switch water sources, one
with more rain water etc, thus changing the KH.

CO2 content is not the only substance that can reduce or affect your pH.
Phosphate is known for altering the pH. Acids leeching from decomposing
dead matter or even drift wood can affect it. So you may need to take
these issues into account.

Nikki