Organic/inorganic doesn't make much of a difference. The structure and chemical composition of the activated carbon is what matters. If the carbon has cations in it's structure it will remove anions like nitrite and nitrate. If it has anions it can remove cations like K and Na. Porosity is a key ingredient in it adsorptive ability. For example if the carbon is mostly large macropores it will adsorb larger molecules more efficiently while the smaller one will pass right through. If the carbon is mostly composed of micropores (densely packed) it will adsorb smaller molecules efficiently and not the larger one.
Since organic and inorganic molecules can be the same size (nitrate and ethanol molar mass both = 62 g per mole) this classification does not apply.
As the nutrients in Fluorish are very small anions and cations and the activated carbon we use in aquariums has large macropores, they will not be easily adsorbed by the carbon.
If you have a planted tank, you don't need carbon. I ahve two planted tanks that have nothing but ceramic bio media in them. Plants are doing a lot for your tank.