Amit wrote:

Hello All,
I have a 100 gallon planted tank.
Since I was adding to much of a CO2 with a PH of 6.2 and KH about 10
(40-45ppm)
I have decreased the CO2 amount from bubble per second to bubble per 5
seconds.
Water parameters are as follows :
PH 7.2
KH 10
GH 12
That leaves us with a CO2 at about 19ppm - Optimal! based on the Chuck CO2
table.

Good job. Try getting the CO2 a bit higher, closer to 25ppm. Maybe 1 bubble per
four seconds?

If I won't use the CO2, My tap water already comes with PH of 7.2 and KH of
10 - does this eliminated my need for a CO2 system ???

No. Water in equilibrium with the atmosphere will have about 3ppm CO2. At a KH
of 10, this means your pH would be 8.0. If it comes out of the tap with pH 7.2,
then it has a higher amount of CO2 already dissolved in it. This is true in
many cities. Try setting tap water out for 24 hours, then measuring the pH.


Do plants do better in a KH between 3-8 ?

And higher. And lower, I've kept many successfully at 2KH. Don't worry about
adjusting KH for your plants.