Well what I've experienced with mosses and DEFINATELY anubias nana, is that they don't need the dosing or ferts! But that's just me, and they might not need any substrate either, but I'm not sure, I grow all mine on rocks and wood.

(I emphisized the anubias because I grew a "FOREST" of it in the back of my tank in two months around 5in. x 5in. with only 3 small plants at the start!)