Miri,
I have to keep on my tank constantly. I have a dosing system that doese kalk all thru out the day. It keeps the SG in check, and the pH is at a constant 8.3. My alk is around 3.5 and this is constant. How are you topping of your tank? I would defenitly suggest kalk for a nano, it helps immensly, IMO. Since I starte dosing my tank has been very stable, actually not much flux has been seen in the past 5 months. I tride dripping kalk at night, but that didn't work. I could never get the right amount of water Vs. evap. So I made the following doser.
DIY Kalk/Top off doser . HTH.
Peace
EK