Why Did My Kh/gh Increase?

[michaelwgroves]

Last time I tested my KH/GH about 6 months ago it was 4dKH and 6dGH
I just tested it again and now it's 8dKH and 11dGH.

The only major chance since the last test is I am injecting Co2.
My Ph was about 8.0, I now maintain it at 6.9

Any idea's?

 

[shelaghfishface]

gee thats a good looking tank how big is it

 

[michaelwgroves]

It's 900 litres, check out my profile for details and pictures

 

[shelaghfishface]

wow, now thats a profile.. beautiful stuff