Hardened, softened and confused...HELP !

The tap water in my area has a carbonate hardness of 1.5dKH. Now, why
should I increase it to at least 3.5dKH, apart from the danger of an
acid drop?

Do plants assimilate better at hardness in the region of 3.5 to 4.0dKH?

But I don't really see any real drop in the pH. With hardness of 1.5dKH,
my pH is in the region of 6.7.

In fact the CO2 table indicated that with hardness of 1.5dKH, the pH
should be in the region of 6.6 to 6.8. And this will tie up to an
optimal CO2 level at 7.0mg/l to 11.1 mg/l

Now, do you experts reckoned I should increase my hardness?

If you are dependant on the CO2 visual test-kit, then I agree that the
hardness should be increased. At hardness below 2.0dKH, the presence of
other acid will fool the CO2 visual test-kit into thinking that CO2 is

But as I am using the Dupla pH Controller, I just need to determine my
hardness, then set the pH to the value in the CO2 table.

Please advise as this is quite confusing.


p/s: Noticed that Amano's hardness in the region of 2-3dKH.