Co2 Not Lowering Ph

[IronChefItaly]

I have a co2 system releasing 1 bubble per second via ceramic diffuser into a 26 gallon tank for 8 hours a day during the photo period. I use tap water for water changes and can't seem to get the pH to lower past 7.8 (highest reading on my pH test). I know the Edmonton water has a fairly high KH but i feel like i may be doing something completely wrong here. I can give more details of my water chemistry if helpful.

I appreciate anyone who takes the time to read this and reply!

[jvision]

What is the purpose of the CO2 - is it to lower pH, or supply plants with needed carbon? If its the latter, aim for 30ppm using the pH/kH graph, or gauge by plan growth and presence of algae. If you're using it to lower pH, make sure your test kit is valid, and if it is, increase your bubble rate.

[ckmullin]

1 bps is low up it to 3 bps and test again after a few hours.

[IronChefItaly]

Thanks for the quick responses! It is for plant growth and i have two different tests for pH. I'll try to bump the bps up to 3 but that seems pretty high for a 26 gal.

Also what is this pH/kH graph?

Just took some measurements and found that the GH and KH is 150 and 180 ppm respectively and the temperature is 26 degrees. (i think temp effects co2 disolving?)

[ckmullin]

There are a few different versions of the same thing but I've always liked this utility:

http://web.archive.org/web/20080601051640/http://www.csd.net/~cgadd/aqua/art_plant_aquacalc.htm

http://web.archive.org/web/20080601051640/http://www.csd.net/~cgadd/download/aquacalc_setup.exe

Don't worry about lowering ph with co2 but rather use co2 to provide carbon. Lowering of ph is a byproduct of using co2.

Edited September 16, 2013 by ckmullin