Amit wrote:

1. Does a CO2 system is actually needed in hard water, assuming water is
replaced every 2 weeks and water parameters will not really change. PH is
rather stable.

Your CO2 system is working fine. If it were not working, your pH would be about
8 at night, reflecting atmospheric equilibrium of about 3ppm CO2 with your 12
KH.

2. Should I target to higher levels of CO2? (well ph will slightly drop and
my crypts will melt...)

22ppm is pretty good.


3. Does any of the other parameters in hard water can effect the CO2
dissolved levels ?

The actual relationship is that the CO2 level and the KH determine the pH,
assuming no pH altering chemicals have been added. Therefore, measuring pH and
KH allow you to deduce your CO2. To answer your question, no other parameters
have a major effect.


4. In hard water levels I know that some plants will have trouble processing
the Macro and Micro nutritients.

Plants prefer hard water to soft water. Calcium and Magnesium, the mojor
components of GH, are necessary plant nutrients. Consider yourself lucky.

5. FE levels are 0 can there be a process which the FE will bind itself to
other thing rather than to plants?

I cannot answer this. Check out the nutirent deficiency charts to see if you
have iron deficiency symptoms:

http://www.csd.net/~cgadd/aqua/art_plant_nutrient.htm


6. Is it correct to link between CO2 levels and hard water or should I look
for a new direction?

What problem are you trying to solve? You said that both plants and fish are
happy. Does this not make you happy too?