I don't add any supplements to my nano at all. I don't trust most of those bottled supplements because you never know what they have in them, and I am a firm believer in knowing exactly what is going into my tank before I put it in there. If they don't have a complete list of ingredients on the side, I won't even consider buying it and most bottled supplements do not list ingredients.
I find that I have fewer problems by doing small weekly water changes in my nano and my levels balance out to where they need to be with that alone.