Duplaplant + KNO3?

Hi everybody,

after a little research on the net I found out that I could add potassium 
nitrate (KNO3) to my tank to prevent nitrate limitation (as in the recipe
of PMDD). Then the plants should be able to use the excess phosphates and
my cyanobacteria should go away.

Q1: I am using the Dupla system. Are there any of you who add KNO3 in addition
    to the Dupla fertilizers to prevent nitrate limitation? Is this a 
    recommended method? Experiences?

Q2: Following the PMDD theory, my tank is not K limited or I wouldn't see 
    the N limitation. George Booth showed that Duplaplant contains 
    some K. What happens to the excess K that I introduce with the KNO3?

Q3: For a 200 l tank to achieve a nitrate level of 5 mg/l should I simply add
    5 * 200 = 1000 mg = 1g of KNO3?

Thanks for your thoughts. Andi from Munich, Germany (where we seem to have the
first spring storms).